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flutter / third_party / libpng / cd11345693fcec821ae754abe1517ff962bc71ec / . / libpng.3
blob: 999ed3934691fb68a4d8a02146a5b7f6e423e62e [file] [log] [blame]
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]1.TH LIBPNG 3 "February 14, 2011"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]3libpng \- Portable Network Graphics (PNG) Reference Library 1.5.2beta02
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4.SH SYNOPSIS
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]5\fI\fB
6
7\fB#include <png.h>\fP
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9\fI\fB
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]10
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]11\fBpng_uint_32 png_access_version_number \fI(void\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]13\fI\fB
14
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]15\fBvoid png_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]17\fI\fB
18
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]19\fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP
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21\fI\fB
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23\fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
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25\fI\fB
26
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]27\fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]29\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]31\fBvoid png_chunk_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]32
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]33\fI\fB
34
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35\fBvoid png_chunk_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]36
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]37\fI\fB
38
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39\fBvoid png_convert_from_struct_tm (png_timep \fP\fIptime\fP\fB, struct tm FAR * \fIttime\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]40
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]41\fI\fB
42
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]43\fBvoid png_convert_from_time_t (png_timep \fP\fIptime\fP\fB, time_t \fIttime\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]44
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]45\fI\fB
46
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]47\fBpng_charp png_convert_to_rfc1123 (png_structp \fP\fIpng_ptr\fP\fB, png_timep \fIptime\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]48
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]49\fI\fB
50
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]51\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]52
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]53\fI\fB
54
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]55\fBpng_structp png_create_read_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]56
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]57\fI\fB
58
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]59\fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]60
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]61\fI\fB
62
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]63\fBpng_structp png_create_write_struct (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarn_fn\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]64
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]65\fI\fB
66
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]67\fBpng_structp png_create_write_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
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69\fI\fB
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71\fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask)\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]72
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]73\fI\fB
74
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]75\fBvoid png_destroy_info_struct (png_structp \fP\fIpng_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]77\fI\fB
78
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]79\fBvoid png_destroy_read_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fP\fIinfo_ptr_ptr\fP\fB, png_infopp \fIend_info_ptr_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]81\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]83\fBvoid png_destroy_write_struct (png_structpp \fP\fIpng_ptr_ptr\fP\fB, png_infopp \fIinfo_ptr_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]85\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]87\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP
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89\fI\fB
90
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]91\fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]93\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]95\fBvoid png_free (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]97\fI\fB
98
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]99\fBvoid png_free_chunk_list (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]101\fI\fB
102
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]103\fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]104
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]105\fI\fB
106
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]107\fBvoid png_free_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fInum\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]108
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]109\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]111\fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]112
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]113\fI\fB
114
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]115\fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]116
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]117\fI\fB
118
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]119\fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]120
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]121\fI\fB
122
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]123\fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]124
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]125\fI\fB
126
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]127\fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]128
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]129\fI\fB
130
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]131\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]132
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]133\fI\fB
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Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]135\fI\fB
136
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]137\fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]138
139\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]141\fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]142
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]143\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]145\fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]146
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]147\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]149\fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]150
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]151\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]153\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]154
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]155\fI\fB
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John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]157\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP
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159\fI\fB
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161\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP
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163\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]165\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]166
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]167\fI\fB
168
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]169\fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]170
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]171\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]173\fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]174
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]175\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]177\fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]178
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]179\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]181\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]182
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]183\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]185\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]186
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]187\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]189\fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]190
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]191\fI\fB
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John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]193\fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]194
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]195\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]197\fBpng_uint_32 png_get_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*width\fP\fB, png_uint_32 \fP\fI*height\fP\fB, int \fP\fI*bit_depth\fP\fB, int \fP\fI*color_type\fP\fB, int \fP\fI*interlace_type\fP\fB, int \fP\fI*compression_type\fP\fB, int \fI*filter_type\fP\fB);\fP
198
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]199\fI\fB
200
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]201\fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]202
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]203\fI\fB
204
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]205\fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]206
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]207\fI\fB
208
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]209\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
210
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]211\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]212
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]213\fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]214
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]215\fI\fB
216
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]217\fBpng_const_bytep png_get_io_chunk_name (png_structp \fIpng_ptr\fP\fB);\fP
218
219\fI\fB
220
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]221\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]222
223\fI\fB
224
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]225\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
226
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]227\fI\fB
228
Glenn Randers-Pehrsona63dbed2011-01-22 08:51:19 -0600[diff] [blame]229\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP
230
231\fI\fB
232
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]233\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]234
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]235\fI\fB
236
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]237\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]238
239\fI\fB
240
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]241\fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]242
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]243\fI\fB
244
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]245\fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]246
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]247\fI\fB
248
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]249\fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]250
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]251\fI\fB
252
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]253\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]254
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]255\fI\fB
256
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]257\fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]258
259\fI\fB
260
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]261\fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]262
263\fI\fB
264
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]265\fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]266
267\fI\fB
268
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]269\fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]270
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]271\fI\fB
272
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]273\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]274
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]275\fI\fB
276
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]277\fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]278
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]279\fI\fB
280
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]281\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr)
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]282
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]283\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]284
285\fI\fB
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]286
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]287\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]288
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]289\fI\fB
290
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]291\fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]292
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]293\fI\fB
294
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]295\fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]296
297\fI\fB
298
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]299\fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]300
301\fI\fB
302
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]303\fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]304
305\fI\fB
306
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]307\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]308
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]309\fI\fB
310
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]311\fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]312
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]313\fI\fB
314
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]315\fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]316
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]317\fI\fB
318
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]319\fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]320
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]321\fI\fB
322
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]323\fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]324
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]325\fI\fB
326
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]327\fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]328
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]329\fI\fB
330
331\fB/* This function is really an inline macro. \fI*/
332
333\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
334
335\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]336
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]337\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]338
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]339\fI\fB
340
341\fB/* This function is really an inline macro. \fI*/
342
343\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
344
345\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]346
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]347\fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]348
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]349\fI\fB
350
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]351\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]352
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]353\fI\fB
354
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]355\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]356
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]357\fI\fB
358
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]359\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]360
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]361\fI\fB
362
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]363\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]364
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]365\fI\fB
366
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]367\fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]368
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]369\fI\fB
370
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]371\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]372
373\fI\fB
374
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]375\fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]376
377\fI\fB
378
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]379\fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]380
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]381\fI\fB
382
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]383\fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]384
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]385\fI\fB
386
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]387\fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]388
389\fI\fB
390
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]391\fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]392
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]393\fI\fB
394
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]395\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]396
397\fI\fB
398
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]399\fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]400
401\fI\fB
402
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]403\fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]404
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]405\fI\fB
406
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]407\fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]408
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]409\fI\fB
410
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]411\fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]412
413\fI\fB
414
John Bowler0a5c9c02011-01-22 17:36:34 -0600[diff] [blame]415\fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]416
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]417\fI\fB
418
Glenn Randers-Pehrsonc1bfe682002-03-06 22:08:00 -0600[diff] [blame]419\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
420
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]421\fI\fB
422
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]423\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP
424
425\fI\fB
426
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]427\fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]428
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]429\fI\fB
430
Glenn Randers-Pehrsonf98726a2010-02-19 09:54:53 -0600[diff] [blame]431\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP
432
433\fI\fB
434
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]435\fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]436
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]437\fI\fB
438
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]439\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
440
441\fI\fB
442
443\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
444
445\fI\fB
446
447\fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]448
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]449\fI\fB
450
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]451\fBvoid png_process_data (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fIbuffer\fP\fB, png_size_t \fIbuffer_size\fP\fB);\fP
452
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]453\fI\fB
454
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]455\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP
456
457\fI\fB
458
459\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP
460
461\fI\fB
462
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]463\fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP
464
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]465\fI\fB
466
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]467\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
468
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]469\fI\fB
470
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]471\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
472
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]473\fI\fB
474
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]475\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
476
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]477\fI\fB
478
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]479\fBvoid png_read_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]480
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]481\fI\fB
482
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]483\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
484
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]485\fI\fB
486
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]487\fBvoid png_read_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_bytepp \fP\fIdisplay_row\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP
488
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]489\fI\fB
490
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]491\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
492
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]493\fI\fB
494
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]495\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP
496
497\fI\fB
498
499\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]500
501\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]502
503\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
504
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]505\fI\fB
506
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]507\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
508
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]509\fI\fB
510
511\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
512
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]513\fI\fB
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]514
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]515\fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP
516
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]517\fI\fB
518
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]519\fBvoid png_set_background_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, png_uint_32 \fIbackground_gamma\fP\fB);\fP
520
521\fI\fB
522
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]523\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP
524
525\fI\fB
526
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]527\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
528
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]529\fI\fB
530
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]531\fBvoid png_set_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fIbackground\fP\fB);\fP
532
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]533\fI\fB
534
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]535\fBvoid png_set_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fIwhite_x\fP\fB, double \fP\fIwhite_y\fP\fB, double \fP\fIred_x\fP\fB, double \fP\fIred_y\fP\fB, double \fP\fIgreen_x\fP\fB, double \fP\fIgreen_y\fP\fB, double \fP\fIblue_x\fP\fB, double \fIblue_y\fP\fB);\fP
536
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]537\fI\fB
538
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]539\fBvoid png_set_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwhite_x\fP\fB, png_uint_32 \fP\fIwhite_y\fP\fB, png_uint_32 \fP\fIred_x\fP\fB, png_uint_32 \fP\fIred_y\fP\fB, png_uint_32 \fP\fIgreen_x\fP\fB, png_uint_32 \fP\fIgreen_y\fP\fB, png_uint_32 \fP\fIblue_x\fP\fB, png_uint_32 \fIblue_y\fP\fB);\fP
540
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]541\fI\fB
542
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]543\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
544
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]545\fI\fB
546
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]547\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
548
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]549\fI\fB
550
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]551\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
552
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]553\fI\fB
554
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]555\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
556
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]557\fI\fB
558
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]559\fBvoid png_set_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]560
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]561\fI\fB
562
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]563\fBvoid png_set_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]564
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]565\fI\fB
566
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]567\fBvoid png_set_crc_action (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIcrit_action\fP\fB, int \fIancil_action\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]568
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]569\fI\fB
570
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]571\fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]572
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]573\fI\fB
574
Glenn Randers-Pehrsonc85f5f62011-02-13 05:56:07 -0600[diff] [blame]575\fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP
576
577\fI\fB
578
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]579\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]580
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]581\fI\fB
582
John Bowler8ea598b2011-02-16 06:09:57 -0600[diff] [blame]583\fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP
584
585\fI\fB
586
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]587\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]588
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]589\fI\fB
590
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]591\fBvoid png_set_filler (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]592
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]593\fI\fB
594
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]595\fBvoid png_set_filter (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImethod\fP\fB, int \fIfilters\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]596
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]597\fI\fB
598
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]599\fBvoid png_set_filter_heuristics (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_doublep \fP\fIfilter_weights\fP\fB, png_doublep \fIfilter_costs\fP\fB);\fP
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]600
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]601\fI\fB
602
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]603\fBvoid png_set_filter_heuristics_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_fixed_point_p \fP\fIfilter_weights\fP\fB, png_fixed_point_p \fIfilter_costs\fP\fB);\fP
604
605\fI\fB
606
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]607\fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]608
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]609\fI\fB
610
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]611\fBvoid png_set_gamma (png_structp \fP\fIpng_ptr\fP\fB, double \fP\fIscreen_gamma\fP\fB, double \fIdefault_file_gamma\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]612
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]613\fI\fB
614
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]615\fBvoid png_set_gamma_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIscreen_gamma\fP\fB, png_uint_32 \fIdefault_file_gamma\fP\fB);\fP
616
617\fI\fB
618
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]619\fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]620
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]621\fI\fB
622
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]623\fBvoid png_set_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIfile_gamma\fP\fB);\fP
624
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]625\fI\fB
626
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]627\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]628
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]629\fI\fB
630
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]631\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]632
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]633\fI\fB
634
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]635\fBvoid png_set_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fIhist\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]636
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]637\fI\fB
638
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]639\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]640
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]641\fI\fB
642
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]643\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]644
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]645\fI\fB
646
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]647\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
648
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]649\fI\fB
650
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]651\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]652
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]653\fI\fB
654
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]655\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]656
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]657\fI\fB
658
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]659\fBvoid png_set_IHDR (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIwidth\fP\fB, png_uint_32 \fP\fIheight\fP\fB, int \fP\fIbit_depth\fP\fB, int \fP\fIcolor_type\fP\fB, int \fP\fIinterlace_type\fP\fB, int \fP\fIcompression_type\fP\fB, int \fIfilter_type\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]660
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]661\fI\fB
662
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]663\fBvoid png_set_keep_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIkeep\fP\fB, png_bytep \fP\fIchunk_list\fP\fB, int \fInum_chunks\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]664
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]665\fI\fB
666
Glenn Randers-Pehrson1e6ed732009-11-20 22:06:56 -0600[diff] [blame]667\fBjmp_buf* png_set_longjmp_fn (png_structp \fP\fIpng_ptr\fP\fB, png_longjmp_ptr \fP\fIlongjmp_fn\fP\fB, size_t \fIjmp_buf_size\fP\fB);\fP
668
669\fI\fB
670
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]671\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP
672
673\fI\fB
674
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]675\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
676
677\fI\fB
678
679\fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]680
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]681\fI\fB
682
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]683\fBvoid png_set_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIoffset_x\fP\fB, png_uint_32 \fP\fIoffset_y\fP\fB, int \fIunit_type\fP\fB);\fP
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]684
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]685\fI\fB
686
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]687\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]688
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]689\fI\fB
690
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]691\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]692
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]693\fI\fB
694
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]695\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]696
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]697\fI\fB
698
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]699\fBvoid png_set_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIpurpose\fP\fB, png_int_32 \fP\fIX0\fP\fB, png_int_32 \fP\fIX1\fP\fB, int \fP\fItype\fP\fB, int \fP\fInparams\fP\fB, png_charp \fP\fIunits\fP\fB, png_charpp \fIparams\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]700
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]701\fI\fB
702
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]703\fBvoid png_set_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fIres_x\fP\fB, png_uint_32 \fP\fIres_y\fP\fB, int \fIunit_type\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]704
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]705\fI\fB
706
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]707\fBvoid png_set_progressive_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIprogressive_ptr\fP\fB, png_progressive_info_ptr \fP\fIinfo_fn\fP\fB, png_progressive_row_ptr \fP\fIrow_fn\fP\fB, png_progressive_end_ptr \fIend_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]708
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]709\fI\fB
710
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]711\fBvoid png_set_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fInum_palette\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]712
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]713\fI\fB
714
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]715\fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP
716
717\fI\fB
718
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]719\fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]720
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]721\fI\fB
722
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]723\fBvoid png_set_read_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_read_status_ptr \fIread_row_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]724
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]725\fI\fB
726
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]727\fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP
728
729\fI\fB
730
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]731\fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]732
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]733\fI\fB
734
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]735\fBvoid png_set_rgb_to_gray (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIerror_action\fP\fB, double \fP\fIred\fP\fB, double \fIgreen\fP\fB);\fP
736
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]737\fI\fB
738
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]739\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]740
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]741\fI\fB
742
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]743\fBvoid png_set_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytepp \fIrow_pointers\fP\fB);\fP
744
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]745\fI\fB
746
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]747\fBvoid png_set_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fIsig_bit\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]748
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]749\fI\fB
750
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]751\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP
752
753\fI\fB
754
755\fBvoid png_set_sCAL_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_fixed_point \fP\fIwidth\fP\fB, png_fixed_point \fIheight\fP\fB);\fP
756
757\fI\fB
758
759\fBvoid png_set_sCAL_s (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_charp \fP\fIwidth\fP\fB, png_charp \fIheight\fP\fB);\fP
760
761\fI\fB
762
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]763\fBvoid png_set_shift (png_structp \fP\fIpng_ptr\fP\fB, png_color_8p \fItrue_bits\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]764
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]765\fI\fB
766
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]767\fBvoid png_set_sig_bytes (png_structp \fP\fIpng_ptr\fP\fB, int \fInum_bytes\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]768
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]769\fI\fB
770
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]771\fBvoid png_set_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fP\fIsplt_ptr\fP\fB, int \fInum_spalettes\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]772
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]773\fI\fB
774
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]775\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]776
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]777\fI\fB
778
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]779\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]780
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]781\fI\fB
782
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]783\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]784
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]785\fI\fB
786
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]787\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]788
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]789\fI\fB
790
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]791\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP
792
793\fI\fB
794
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]795\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]796
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]797\fI\fB
798
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]799\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]800
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]801\fI\fB
802
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]803\fBvoid png_set_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fItext_ptr\fP\fB, int \fInum_text\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]804
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]805\fI\fB
806
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]807\fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]808
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]809\fI\fB
810
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]811\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]812
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]813\fI\fB
814
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]815\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]816
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]817\fI\fB
818
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]819\fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP
820
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]821\fI\fB
822
Glenn Randers-Pehrsonbb98bcb2011-01-22 16:27:39 -0600[diff] [blame]823\fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]824
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]825\fI\fB
826
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]827\fBvoid png_set_user_limits (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIuser_width_max\fP\fB, png_uint_32 \fIuser_height_max\fP\fB);\fP
828
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]829\fI\fB
830
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]831\fBvoid png_set_user_transform_info (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_transform_ptr\fP\fB, int \fP\fIuser_transform_depth\fP\fB, int \fIuser_transform_channels\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]832
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]833\fI\fB
834
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]835\fBvoid png_set_write_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fP\fIwrite_data_fn\fP\fB, png_flush_ptr \fIoutput_flush_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]836
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]837\fI\fB
838
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]839\fBvoid png_set_write_status_fn (png_structp \fP\fIpng_ptr\fP\fB, png_write_status_ptr \fIwrite_row_fn\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]840
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]841\fI\fB
842
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]843\fBvoid png_set_write_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIwrite_user_transform_fn\fP\fB);\fP
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]844
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]845\fI\fB
846
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]847\fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]848
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]849\fI\fB
850
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]851\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]852
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]853\fI\fB
854
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]855\fBvoid png_warning (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fImessage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]856
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]857\fI\fB
858
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]859\fBvoid png_write_chunk (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]860
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]861\fI\fB
862
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]863\fBvoid png_write_chunk_data (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIdata\fP\fB, png_size_t \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]864
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]865\fI\fB
866
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]867\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]868
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]869\fI\fB
870
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]871\fBvoid png_write_chunk_start (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIchunk_name\fP\fB, png_uint_32 \fIlength\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]872
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]873\fI\fB
874
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]875\fBvoid png_write_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]876
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]877\fI\fB
878
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]879\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]880
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]881\fI\fB
882
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]883\fBvoid png_write_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]884
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]885\fI\fB
886
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]887\fBvoid png_write_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]888
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]889\fI\fB
890
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]891\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
892
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]893\fI\fB
894
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]895\fBvoid png_write_png (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fItransforms\fP\fB, png_voidp \fIparams\fP\fB);\fP
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]896
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]897\fI\fB
898
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]899\fBvoid png_write_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIrow\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]900
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]901\fI\fB
902
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]903\fBvoid png_write_rows (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fP\fIrow\fP\fB, png_uint_32 \fInum_rows\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]904
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]905\fI\fB
906
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]907\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
908
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]909\fI\fB
910
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]911\fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP
912
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]913\fI\fB
914
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]915\fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP
916
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]917\fI\fB
918
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]919.SH DESCRIPTION
920The
921.I libpng
922library supports encoding, decoding, and various manipulations of
923the Portable Network Graphics (PNG) format image files. It uses the
924.IR zlib(3)
925compression library.
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]926Following is a copy of the libpng-manual.txt file that accompanies libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]927.SH LIBPNG.TXT
Glenn Randers-Pehrson557b2562010-10-17 12:55:04 -0500[diff] [blame]928libpng-manual.txt - A description on how to use and modify libpng
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]929
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]930 libpng version 1.5.2beta02 - February 14, 2011
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]931 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]932 <glennrp at users.sourceforge.net>
Glenn Randers-Pehrson9f45c8e2011-01-15 19:35:03 -0600[diff] [blame]933 Copyright (c) 1998-2011 Glenn Randers-Pehrson
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]934
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]935 This document is released under the libpng license.
Glenn Randers-Pehrsonc332bbc2009-06-25 13:43:50 -0500[diff] [blame]936 For conditions of distribution and use, see the disclaimer
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]937 and license in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]938
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]939 Based on:
940
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]941 libpng versions 0.97, January 1998, through 1.5.2beta02 - February 14, 2011
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]942 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson9f45c8e2011-01-15 19:35:03 -0600[diff] [blame]943 Copyright (c) 1998-2011 Glenn Randers-Pehrson
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]944
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]945 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]946 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]947 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]948
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]949 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]950 For conditions of distribution and use, see copyright
951 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]952 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]953
954 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]955 Copyright (c) 1995, 1996 Frank J. T. Wojcik
956 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]957
958.SH I. Introduction
959
960This file describes how to use and modify the PNG reference library
961(known as libpng) for your own use. There are five sections to this
962file: introduction, structures, reading, writing, and modification and
963configuration notes for various special platforms. In addition to this
964file, example.c is a good starting point for using the library, as
965it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]966will need. We assume that libpng is already installed; see the
967INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]968
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]969For examples of libpng usage, see the files "example.c", "pngtest.c",
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]970and the files in the "contrib" directory, all of which are included in
971the libpng distribution.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]972
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]973Libpng was written as a companion to the PNG specification, as a way
974of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]975file format in application programs.
976
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]977The PNG specification (second edition), November 2003, is available as
978a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at
979<http://www.w3.org/TR/2003/REC-PNG-20031110/
980The W3C and ISO documents have identical technical content.
981
982The PNG-1.2 specification is available at
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]983<http://www.libpng.org/pub/png/documents/>. It is technically equivalent
984to the PNG specification (second edition) but has some additional material.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]985
986The PNG-1.0 specification is available
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]987as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]988W3C Recommendation <http://www.w3.org/TR/REC.png.html>.
989
990Some additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]991documents at <http://www.libpng.org/pub/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]992
993Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]994about PNG, and the latest version of libpng, can be found at the PNG home
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]995page, <http://www.libpng.org/pub/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]996
997Most users will not have to modify the library significantly; advanced
998users may want to modify it more. All attempts were made to make it as
999complete as possible, while keeping the code easy to understand.
1000Currently, this library only supports C. Support for other languages
1001is being considered.
1002
1003Libpng has been designed to handle multiple sessions at one time,
1004to be easily modifiable, to be portable to the vast majority of
1005machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
1006to use. The ultimate goal of libpng is to promote the acceptance of
1007the PNG file format in whatever way possible. While there is still
1008work to be done (see the TODO file), libpng should cover the
1009majority of the needs of its users.
1010
1011Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1012Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1013be found at the zlib home page, <http://www.info-zip.org/pub/infozip/zlib/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1014The zlib compression utility is a general purpose utility that is
1015useful for more than PNG files, and can be used without libpng.
1016See the documentation delivered with zlib for more details.
1017You can usually find the source files for the zlib utility wherever you
1018find the libpng source files.
1019
1020Libpng is thread safe, provided the threads are using different
1021instances of the structures. Each thread should have its own
1022png_struct and png_info instances, and thus its own image.
1023Libpng does not protect itself against two threads using the
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1024same instance of a structure.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1025
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1026.SH II. Structures
1027
1028There are two main structures that are important to libpng, png_struct
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1029and png_info. Both are internal structures that are no longer exposed
1030in the libpng interface (as of libpng 1.5.0).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1031
1032The png_info structure is designed to provide information about the
1033PNG file. At one time, the fields of png_info were intended to be
1034directly accessible to the user. However, this tended to cause problems
1035with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]1036a set of interface functions for png_info (the png_get_*() and png_set_*()
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1037functions) was developed.
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]1038
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1039The png_struct structure is the object used by the library to decode a
1040single image. As of 1.5.0 this structure is also not exposed.
1041
1042Almost all libpng APIs require a pointer to a png_struct as the first argument.
1043Many (in particular the png_set and png_get APIs) also require a pointer
1044to png_info as the second argument. Some application visible macros
1045defined in png.h designed for basic data access (reading and writing
1046integers in the PNG format) break this rule, but it's almost always safe
1047to assume that a (png_struct*) has to be passed to call an API function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1048
1049The png.h header file is an invaluable reference for programming with libpng.
1050And while I'm on the topic, make sure you include the libpng header file:
1051
1052#include <png.h>
1053
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1054.SS Types
1055
1056The png.h header file defines a number of integral types used by the
1057APIs. Most of these are fairly obvious; for example types corresponding
1058to integers of particular sizes and types for passing color values.
1059
1060One exception is how non-integral numbers are handled. For application
1061convenience most APIs that take such numbers have C (double) arguments,
1062however internally PNG, and libpng, use 32 bit signed integers and encode
1063the value by multiplying by 100,000. As of libpng 1.5.0 a convenience
1064macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point)
1065which is simply (png_int_32).
1066
1067All APIs that take (double) arguments also have an matching API that
1068takes the corresponding fixed point integer arguments. The fixed point
1069API has the same name as the floating point one with _fixed appended.
1070The actual range of values permitted in the APIs is frequently less than
1071the full range of (png_fixed_point) (-21474 to +21474). When APIs require
1072a non-negative argument the type is recorded as png_uint_32 above. Consult
1073the header file and the text below for more information.
1074
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]1075Special care must be take with sCAL chunk handling because the chunk itself
1076uses non-integral values encoded as strings containing decimal floating point
1077numbers. See the comments in the header file.
1078
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]1079.SS Configuration
1080
1081The main header file function declarations are frequently protected by C
1082preprocessing directives of the form:
1083
1084 #ifdef PNG_feature_SUPPORTED
1085 declare-function
1086 #endif
1087
1088The library can be built without support for these APIs, although a
1089standard build will have all implemented APIs. Application programs
1090should check the feature macros before using an API for maximum
1091portability. From libpng 1.5.0 the feature macros set during the build
1092of libpng are recorded in the header file "pnglibconf.h" and this file
1093is always included by png.h.
1094
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]1095If you don't need to change the library configuration from the default skip to
1096the next section ("Reading").
1097
1098Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all
1099of the build project files in the 'projects' directory simply copy
1100scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build
1101systems do not permit easy auto-configuration of the library - they only
1102support the default configuration.
1103
1104The easiest way to make minor changes to the libpng configuration when
1105auto-configuration is supported is to add definitions to the command line
1106using (typically) CPPFLAGS. For example:
1107
1108CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC
1109
1110will change the internal libpng math implementation for gamma correction and
1111other arithmetic calculations to fixed point, avoiding the need for fast
1112floating point support. The result can be seen in the generated pnglibconf.h -
1113make sure it contains the changed feature macro setting.
1114
1115If you need to make more extensive configuration changes - more than one or two
1116feature macro settings - you can either add -DPNG_USER_CONFIG to the build
1117command line and put a list of feature macro settings in pngusr.h or you can set
1118DFA_XTRA (a makefile variable) to a file containing the same information in the
1119form of 'option' settings.
1120
1121A. Changing pnglibconf.h
1122
1123A variety of methods exist to build libpng. Not all of these support
1124reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be
1125rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand.
1126
1127Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing
1128the lines defining the supported features, paying very close attention to the
1129'option' information in scripts/pnglibconf.dfa that describes those features and
1130their requirements. This is easy to get wrong.
1131
1132B. Configuration using DFA_XTRA
1133
1134Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later
1135variant such as 'nawk' or 'gawk', is available. The configure build will
1136automatically find an appropriate awk and build pnglibconf.h.
1137scripts/pnglibconf.mak contains a set of make rules for doing the same thing if
1138configure is not used, and many of the makefiles in the scripts directory use
1139this approach.
1140
1141When rebuilding simply write new file containing changed options and set
1142DFA_XTRA to the name of this file. This causes the build to append the new file
1143to the end of scripts/pnglibconf.dfa. pngusr.dfa should contain lines of the
1144following forms:
1145
1146everything = off
1147
1148This turns all optional features off. Include it at the start of pngusr.dfa to
1149make it easier to build a minimal configuration. You will need to turn at least
1150some features on afterward to enable either reading or writing code, or both.
1151
1152option feature on
1153option feature off
1154
1155Enable or disable a single feature. This will automatically enable other
1156features required by a feature that is turned on or disable other features that
1157require a feature which is turned off. Conflicting settings will cause an error
1158message to be emitted by awk.
1159
1160setting feature default value
1161
1162Changes the default value of setting 'feature' to 'value'. There are a small
1163number of settings listed at the top of pnglibconf.h, they are documented in the
1164source code. Most of these values have performance implications for the library
1165but most of them have no visible effect on the API. Some can also be overridden
1166from the API.
1167
1168C. Configuration using PNG_USR_CONFIG
1169
1170If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file
1171pngusr.h will automatically be included before the options in
1172scripts/pnglibconf.dfa are processed. pngusr.h should contain only macro
1173definitions turning features on or off or setting settings.
1174
1175Apart from the global setting "everything = off" all the options listed above
1176can be set using macros in pngusr.h:
1177
1178#define PNG_feature_SUPPORTED
1179
1180is equivalent to:
1181
1182option feature on
1183
1184#define PNG_NO_feature
1185
1186is equivalent to:
1187
1188option feature off
1189
1190#define PNG_feature value
1191
1192is equivalent to:
1193
1194setting feature default value
1195
1196Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the
1197pngusr file you supply override the contents of scripts/pnglibconf.dfa
1198
1199If confusing or incomprehensible behavior results it is possible to
1200examine the intermediate file pnglibconf.dfn to find the full set of
1201dependency information for each setting and option. Simply locate the
1202feature in the file and read the C comments that precede it.
1203
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1204.SH III. Reading
1205
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1206We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1207in a PNG file sequentially, briefly explaining the syntax and purpose
1208of each one. See example.c and png.h for more detail. While
1209progressive reading is covered in the next section, you will still
1210need some of the functions discussed in this section to read a PNG
1211file.
1212
1213.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1214
1215You will want to do the I/O initialization(*) before you get into libpng,
1216so if it doesn't work, you don't have much to undo. Of course, you
1217will also want to insure that you are, in fact, dealing with a PNG
1218file. Libpng provides a simple check to see if a file is a PNG file.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1219To use it, pass in the first 1 to 8 bytes of the file to the function
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]1220png_sig_cmp(), and it will return 0 (false) if the bytes match the
1221corresponding bytes of the PNG signature, or nonzero (true) otherwise.
1222Of course, the more bytes you pass in, the greater the accuracy of the
1223prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1224
1225If you are intending to keep the file pointer open for use in libpng,
1226you must ensure you don't read more than 8 bytes from the beginning
1227of the file, and you also have to make a call to png_set_sig_bytes_read()
1228with the number of bytes you read from the beginning. Libpng will
1229then only check the bytes (if any) that your program didn't read.
1230
1231(*): If you are not using the standard I/O functions, you will need
1232to replace them with custom functions. See the discussion under
1233Customizing libpng.
1234
1235
1236 FILE *fp = fopen(file_name, "rb");
1237 if (!fp)
1238 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1239 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1240 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1241
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1242 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]1243 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1244
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1245 if (!is_png)
1246 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1247 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1248 }
1249
1250
1251Next, png_struct and png_info need to be allocated and initialized. In
1252order to ensure that the size of these structures is correct even with a
1253dynamically linked libpng, there are functions to initialize and
1254allocate the structures. We also pass the library version, optional
1255pointers to error handling functions, and a pointer to a data struct for
1256use by the error functions, if necessary (the pointer and functions can
1257be NULL if the default error handlers are to be used). See the section
1258on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1259The structure allocation functions quietly return NULL if they fail to
1260create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1261
1262 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1263 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1264 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1265
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1266 if (!png_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1267 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1268
1269 png_infop info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1270
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1271 if (!info_ptr)
1272 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1273 png_destroy_read_struct(&png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1274 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1275 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1276 }
1277
1278 png_infop end_info = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1279
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1280 if (!end_info)
1281 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1282 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1283 (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1284 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1285 }
1286
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1287If you want to use your own memory allocation routines,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1288use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1289png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1290
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1291 png_structp png_ptr = png_create_read_struct_2
1292 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
1293 user_error_fn, user_warning_fn, (png_voidp)
1294 user_mem_ptr, user_malloc_fn, user_free_fn);
1295
1296The error handling routines passed to png_create_read_struct()
1297and the memory alloc/free routines passed to png_create_struct_2()
1298are only necessary if you are not using the libpng supplied error
1299handling and memory alloc/free functions.
1300
1301When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1302to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1303your png_jmpbuf(png_ptr). If you read the file from different
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1304routines, you will need to update the jmpbuf field every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1305a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1306
1307See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1308information on setjmp/longjmp. See the discussion on libpng error
1309handling in the Customizing Libpng section below for more information
1310on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1311back to your setjmp, you will want to call png_destroy_read_struct() to
1312free any memory.
1313
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1314 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1315 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1316 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1317 &end_info);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1318 fclose(fp);
1319 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1320 }
1321
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1322If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]1323you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1324errors will result in a call to PNG_ABORT() which defaults to abort().
1325
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]1326You can #define PNG_ABORT() to a function that does something
1327more useful than abort(), as long as your function does not
1328return.
1329
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1330Now you need to set up the input code. The default for libpng is to
1331use the C function fread(). If you use this, you will need to pass a
1332valid FILE * in the function png_init_io(). Be sure that the file is
1333opened in binary mode. If you wish to handle reading data in another
1334way, you need not call the png_init_io() function, but you must then
1335implement the libpng I/O methods discussed in the Customizing Libpng
1336section below.
1337
1338 png_init_io(png_ptr, fp);
1339
1340If you had previously opened the file and read any of the signature from
1341the beginning in order to see if this was a PNG file, you need to let
1342libpng know that there are some bytes missing from the start of the file.
1343
1344 png_set_sig_bytes(png_ptr, number);
1345
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]1346You can change the zlib compression buffer size to be used while
1347reading compressed data with
1348
1349 png_set_compression_buffer_size(png_ptr, buffer_size);
1350
1351where the default size is 8192 bytes. Note that the buffer size
1352is changed immediately and the buffer is reallocated immediately,
1353instead of setting a flag to be acted upon later.
1354
Glenn Randers-Pehrson9dd1cdf2011-01-06 21:42:36 -0600[diff] [blame]1355If you want CRC errors to be handled in a different manner than
1356the default, use
1357
1358 png_set_crc_action(png_ptr, crit_action, ancil_action);
1359
1360The values for png_set_crc_action() say how libpng is to handle CRC errors in
1361ancillary and critical chunks, and whether to use the data contained
1362therein. Note that it is impossible to "discard" data in a critical
1363chunk.
1364
1365Choices for (int) crit_action are
1366 PNG_CRC_DEFAULT 0 error/quit
1367 PNG_CRC_ERROR_QUIT 1 error/quit
1368 PNG_CRC_WARN_USE 3 warn/use data
1369 PNG_CRC_QUIET_USE 4 quiet/use data
1370 PNG_CRC_NO_CHANGE 5 use the current value
1371
1372Choices for (int) ancil_action are
1373 PNG_CRC_DEFAULT 0 error/quit
1374 PNG_CRC_ERROR_QUIT 1 error/quit
1375 PNG_CRC_WARN_DISCARD 2 warn/discard data
1376 PNG_CRC_WARN_USE 3 warn/use data
1377 PNG_CRC_QUIET_USE 4 quiet/use data
1378 PNG_CRC_NO_CHANGE 5 use the current value
1379
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1380.SS Setting up callback code
1381
1382You can set up a callback function to handle any unknown chunks in the
1383input stream. You must supply the function
1384
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]1385 read_chunk_callback(png_structp png_ptr,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1386 png_unknown_chunkp chunk);
1387 {
1388 /* The unknown chunk structure contains your
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1389 chunk data, along with similar data for any other
1390 unknown chunks: */
1391
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1392 png_byte name[5];
1393 png_byte *data;
1394 png_size_t size;
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1395
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1396 /* Note that libpng has already taken care of
1397 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1398
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1399 /* put your code here. Search for your chunk in the
1400 unknown chunk structure, process it, and return one
1401 of the following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1402
1403 return (-n); /* chunk had an error */
1404 return (0); /* did not recognize */
1405 return (n); /* success */
1406 }
1407
1408(You can give your function another name that you like instead of
1409"read_chunk_callback")
1410
1411To inform libpng about your function, use
1412
1413 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1414 read_chunk_callback);
1415
1416This names not only the callback function, but also a user pointer that
1417you can retrieve with
1418
1419 png_get_user_chunk_ptr(png_ptr);
1420
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1421If you call the png_set_read_user_chunk_fn() function, then all unknown
1422chunks will be saved when read, in case your callback function will need
1423one or more of them. This behavior can be changed with the
1424png_set_keep_unknown_chunks() function, described below.
1425
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1426At this point, you can set up a callback function that will be
1427called after each row has been read, which you can use to control
1428a progress meter or the like. It's demonstrated in pngtest.c.
1429You must supply a function
1430
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]1431 void read_row_callback(png_structp png_ptr,
1432 png_uint_32 row, int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1433 {
1434 /* put your code here */
1435 }
1436
1437(You can give it another name that you like instead of "read_row_callback")
1438
1439To inform libpng about your function, use
1440
1441 png_set_read_status_fn(png_ptr, read_row_callback);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1442
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1443.SS Unknown-chunk handling
1444
1445Now you get to set the way the library processes unknown chunks in the
1446input PNG stream. Both known and unknown chunks will be read. Normal
1447behavior is that known chunks will be parsed into information in
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1448various info_ptr members while unknown chunks will be discarded. This
1449behavior can be wasteful if your application will never use some known
1450chunk types. To change this, you can call:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1451
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]1452 png_set_keep_unknown_chunks(png_ptr, keep,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1453 chunk_list, num_chunks);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1454 keep - 0: default unknown chunk handling
1455 1: ignore; do not keep
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1456 2: keep only if safe-to-copy
1457 3: keep even if unsafe-to-copy
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1458
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1459 You can use these definitions:
1460 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1461 PNG_HANDLE_CHUNK_NEVER 1
1462 PNG_HANDLE_CHUNK_IF_SAFE 2
1463 PNG_HANDLE_CHUNK_ALWAYS 3
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1464
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1465 chunk_list - list of chunks affected (a byte string,
1466 five bytes per chunk, NULL or '\0' if
1467 num_chunks is 0)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1468
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1469 num_chunks - number of chunks affected; if 0, all
Glenn Randers-Pehrsondff799e2004-08-07 21:42:49 -0500[diff] [blame]1470 unknown chunks are affected. If nonzero,
1471 only the chunks in the list are affected
1472
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1473Unknown chunks declared in this way will be saved as raw data onto a
1474list of png_unknown_chunk structures. If a chunk that is normally
1475known to libpng is named in the list, it will be handled as unknown,
1476according to the "keep" directive. If a chunk is named in successive
1477instances of png_set_keep_unknown_chunks(), the final instance will
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1478take precedence. The IHDR and IEND chunks should not be named in
1479chunk_list; if they are, libpng will process them normally anyway.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1480
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1481Here is an example of the usage of png_set_keep_unknown_chunks(),
1482where the private "vpAg" chunk will later be processed by a user chunk
1483callback function:
1484
1485 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
1486
1487 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1488 png_byte unused_chunks[]=
1489 {
1490 104, 73, 83, 84, (png_byte) '\0', /* hIST */
1491 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
1492 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
1493 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
1494 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
1495 116, 73, 77, 69, (png_byte) '\0', /* tIME */
1496 };
1497 #endif
1498
1499 ...
1500
1501 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1502 /* ignore all unknown chunks: */
1503 png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1504
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1505 /* except for vpAg: */
1506 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1507
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1508 /* also ignore unused known chunks: */
1509 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
1510 (int)sizeof(unused_chunks)/5);
1511 #endif
1512
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1513.SS User limits
1514
1515The PNG specification allows the width and height of an image to be as
1516large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
1517Since very few applications really need to process such large images,
1518we have imposed an arbitrary 1-million limit on rows and columns.
1519Larger images will be rejected immediately with a png_error() call. If
1520you wish to override this limit, you can use
1521
1522 png_set_user_limits(png_ptr, width_max, height_max);
1523
1524to set your own limits, or use width_max = height_max = 0x7fffffffL
1525to allow all valid dimensions (libpng may reject some very large images
1526anyway because of potential buffer overflow conditions).
1527
1528You should put this statement after you create the PNG structure and
1529before calling png_read_info(), png_read_png(), or png_process_data().
1530If you need to retrieve the limits that are being applied, use
1531
1532 width_max = png_get_user_width_max(png_ptr);
1533 height_max = png_get_user_height_max(png_ptr);
1534
1535The PNG specification sets no limit on the number of ancillary chunks
1536allowed in a PNG datastream. You can impose a limit on the total number
1537of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
1538
1539 png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
1540
1541where 0x7fffffffL means unlimited. You can retrieve this limit with
1542
1543 chunk_cache_max = png_get_chunk_cache_max(png_ptr);
1544
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1545This limit also applies to the number of buffers that can be allocated
1546by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks.
1547
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]1548You can also set a limit on the amount of memory that a compressed chunk
1549other than IDAT can occupy, with
1550
1551 png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max);
1552
1553and you can retrieve the limit with
1554
1555 chunk_malloc_max = png_get_chunk_malloc_max(png_ptr);
1556
1557Any chunks that would cause either of these limits to be exceeded will
1558be ignored.
1559
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1560.SS The high-level read interface
1561
1562At this point there are two ways to proceed; through the high-level
1563read interface, or through a sequence of low-level read operations.
1564You can use the high-level interface if (a) you are willing to read
1565the entire image into memory, and (b) the input transformations
1566you want to do are limited to the following set:
1567
1568 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1569 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
1570 8 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1571 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1572 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1573 samples to bytes
1574 PNG_TRANSFORM_PACKSWAP Change order of packed
1575 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1576 PNG_TRANSFORM_EXPAND Perform set_expand()
1577 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1578 PNG_TRANSFORM_SHIFT Normalize pixels to the
1579 sBIT depth
1580 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1581 to BGRA
1582 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1583 to AG
1584 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1585 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1586 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]1587 PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
1588 to RGB (or GA to RGBA)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1589
1590(This excludes setting a background color, doing gamma transformation,
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]1591quantizing, and setting filler.) If this is the case, simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1592
1593 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1594
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1595where png_transforms is an integer containing the bitwise OR of some
1596set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1597followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1598then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1599
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1600(The final parameter of this call is not yet used. Someday it might point
1601to transformation parameters required by some future input transform.)
1602
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]1603You must use png_transforms and not call any png_set_transform() functions
1604when you use png_read_png().
1605
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1606After you have called png_read_png(), you can retrieve the image data
1607with
1608
1609 row_pointers = png_get_rows(png_ptr, info_ptr);
1610
1611where row_pointers is an array of pointers to the pixel data for each row:
1612
1613 png_bytep row_pointers[height];
1614
1615If you know your image size and pixel size ahead of time, you can allocate
1616row_pointers prior to calling png_read_png() with
1617
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1618 if (height > PNG_UINT_32_MAX/png_sizeof(png_byte))
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1619 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1620 "Image is too tall to process in memory");
1621
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1622 if (width > PNG_UINT_32_MAX/pixel_size)
1623 png_error (png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1624 "Image is too wide to process in memory");
1625
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1626 row_pointers = png_malloc(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1627 height*png_sizeof(png_bytep));
1628
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1629 for (int i=0; i<height, i++)
1630 row_pointers[i]=NULL; /* security precaution */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1631
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1632 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1633 row_pointers[i]=png_malloc(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1634 width*pixel_size);
1635
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1636 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1637
1638Alternatively you could allocate your image in one big block and define
1639row_pointers[i] to point into the proper places in your block.
1640
1641If you use png_set_rows(), the application is responsible for freeing
1642row_pointers (and row_pointers[i], if they were separately allocated).
1643
1644If you don't allocate row_pointers ahead of time, png_read_png() will
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1645do it, and it'll be free'ed by libpng when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1646
1647.SS The low-level read interface
1648
1649If you are going the low-level route, you are now ready to read all
1650the file information up to the actual image data. You do this with a
1651call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1652
1653 png_read_info(png_ptr, info_ptr);
1654
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1655This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1656
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1657.SS Querying the info structure
1658
1659Functions are used to get the information from the info_ptr once it
1660has been read. Note that these fields may not be completely filled
1661in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1662
1663 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1664 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1665 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1666
1667 width - holds the width of the image
1668 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1669
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1670 height - holds the height of the image
1671 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1672
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1673 bit_depth - holds the bit depth of one of the
1674 image channels. (valid values are
1675 1, 2, 4, 8, 16 and depend also on
1676 the color_type. See also
1677 significant bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1678
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1679 color_type - describes which color/alpha channels
1680 are present.
1681 PNG_COLOR_TYPE_GRAY
1682 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1683 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1684 (bit depths 8, 16)
1685 PNG_COLOR_TYPE_PALETTE
1686 (bit depths 1, 2, 4, 8)
1687 PNG_COLOR_TYPE_RGB
1688 (bit_depths 8, 16)
1689 PNG_COLOR_TYPE_RGB_ALPHA
1690 (bit_depths 8, 16)
1691
1692 PNG_COLOR_MASK_PALETTE
1693 PNG_COLOR_MASK_COLOR
1694 PNG_COLOR_MASK_ALPHA
1695
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1696 interlace_type - (PNG_INTERLACE_NONE or
1697 PNG_INTERLACE_ADAM7)
1698
1699 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1700 for PNG 1.0)
1701
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1702 filter_method - (must be PNG_FILTER_TYPE_BASE
1703 for PNG 1.0, and can also be
1704 PNG_INTRAPIXEL_DIFFERENCING if
1705 the PNG datastream is embedded in
1706 a MNG-1.0 datastream)
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1707
1708 Any or all of interlace_type, compression_type, or
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1709 filter_method can be NULL if you are
1710 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1711
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1712 Note that png_get_IHDR() returns 32-bit data into
1713 the application's width and height variables.
1714 This is an unsafe situation if these are 16-bit
1715 variables. In such situations, the
1716 png_get_image_width() and png_get_image_height()
1717 functions described below are safer.
1718
1719 width = png_get_image_width(png_ptr,
1720 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1721
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1722 height = png_get_image_height(png_ptr,
1723 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1724
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1725 bit_depth = png_get_bit_depth(png_ptr,
1726 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1727
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1728 color_type = png_get_color_type(png_ptr,
1729 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1730
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1731 interlace_type = png_get_interlace_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1732 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1733
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1734 compression_type = png_get_compression_type(png_ptr,
1735 info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1736
Glenn Randers-Pehrson2cb633b2011-01-21 08:31:29 -0600[diff] [blame]1737 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrson0bfb58f2009-09-30 23:07:22 -0500[diff] [blame]1738 info_ptr);
1739
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1740 channels = png_get_channels(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1741
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1742 channels - number of channels of info for the
1743 color type (valid values are 1 (GRAY,
1744 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1745 4 (RGB_ALPHA or RGB + filler byte))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1746
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1747 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1748
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1749 rowbytes - number of bytes needed to hold a row
1750
1751 signature = png_get_signature(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1752
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1753 signature - holds the signature read from the
1754 file (if any). The data is kept in
1755 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1756 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1757 application had already read in 4
1758 bytes of signature before starting
1759 libpng, the remaining 4 bytes would
1760 be in signature[4] through signature[7]
1761 (see png_set_sig_bytes())).
1762
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1763These are also important, but their validity depends on whether the chunk
1764has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1765png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1766data has been read, or zero if it is missing. The parameters to the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]1767png_get_<chunk> are set directly if they are simple data types, or a
1768pointer into the info_ptr is returned for any complex types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1769
1770 png_get_PLTE(png_ptr, info_ptr, &palette,
1771 &num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1772
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1773 palette - the palette for the file
1774 (array of png_color)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1775
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1776 num_palette - number of entries in the palette
1777
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1778 png_get_gAMA(png_ptr, info_ptr, &file_gamma);
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame]1779 png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1780
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]1781 file_gamma - the gamma at which the file is
1782 written (PNG_INFO_gAMA)
1783
1784 int_file_gamma - 100,000 times the gamma at which the
1785 file is written
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1786
1787 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1788
Glenn Randers-Pehrson27742382011-01-27 09:37:34 -0600[diff] [blame]1789 file_srgb_intent - the rendering intent (PNG_INFO_sRGB)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1790 The presence of the sRGB chunk
1791 means that the pixel data is in the
1792 sRGB color space. This chunk also
1793 implies specific values of gAMA and
1794 cHRM.
1795
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1796 png_get_iCCP(png_ptr, info_ptr, &name,
1797 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1798
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1799 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1800
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1801 compression_type - The compression type; always
1802 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1803 You may give NULL to this argument to
1804 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1805
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1806 profile - International Color Consortium color
1807 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1808
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]1809 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1810
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1811 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1812
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1813 sig_bit - the number of significant bits for
1814 (PNG_INFO_sBIT) each of the gray,
1815 red, green, and blue channels,
1816 whichever are appropriate for the
1817 given color type (png_color_16)
1818
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1819 png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
1820 &num_trans, &trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1821
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1822 trans_alpha - array of alpha (transparency)
1823 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1824
Glenn Randers-Pehrsonf3c51e42011-01-15 10:25:25 -0600[diff] [blame]1825 num_trans - number of transparent entries
1826 (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1827
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1828 trans_color - graylevel or color sample values of
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1829 the single transparent color for
1830 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1831
1832 png_get_hIST(png_ptr, info_ptr, &hist);
1833 (PNG_INFO_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1834
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1835 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1836 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1837
1838 png_get_tIME(png_ptr, info_ptr, &mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1839
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1840 mod_time - time image was last modified
1841 (PNG_VALID_tIME)
1842
1843 png_get_bKGD(png_ptr, info_ptr, &background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1844
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1845 background - background color (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1846 valid 16-bit red, green and blue
1847 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1848
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1849 num_comments = png_get_text(png_ptr, info_ptr,
1850 &text_ptr, &num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1851
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1852 num_comments - number of comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1853
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1854 text_ptr - array of png_text holding image
1855 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1856
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1857 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1858 on "text" PNG_TEXT_COMPRESSION_NONE
1859 PNG_TEXT_COMPRESSION_zTXt
1860 PNG_ITXT_COMPRESSION_NONE
1861 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1862
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1863 text_ptr[i].key - keyword for comment. Must contain
1864 1-79 characters.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1865
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1866 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1867 keyword. Can be empty.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1868
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1869 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1870 after decompression, 0 for iTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1871
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1872 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1873 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1874
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1875 text_ptr[i].lang - language of comment (empty
1876 string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1877
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1878 text_ptr[i].lang_key - keyword in UTF-8
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1879 (empty string for unknown).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1880
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]1881 Note that the itxt_length, lang, and lang_key
1882 members of the text_ptr structure only exist
1883 when the library is built with iTXt chunk support.
1884
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1885 num_text - number of comments (same as
1886 num_comments; you can put NULL here
1887 to avoid the duplication)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1888
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1889 Note while png_set_text() will accept text, language,
1890 and translated keywords that can be NULL pointers, the
1891 structure returned by png_get_text will always contain
1892 regular zero-terminated C strings. They might be
1893 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1894
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1895 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1896 &palette_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1897
1898 num_spalettes - number of sPLT chunks read.
1899
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1900 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1901 contents of one or more sPLT chunks
1902 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1903
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1904 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1905 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1906
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1907 offset_x - positive offset from the left edge
1908 of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1909
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1910 offset_y - positive offset from the top edge
1911 of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1912
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1913 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1914
1915 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1916 &unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1917
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1918 res_x - pixels/unit physical resolution in
1919 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1920
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1921 res_y - pixels/unit physical resolution in
1922 x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1923
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1924 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1925 PNG_RESOLUTION_METER
1926
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1927 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1928 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1929
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1930 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1931
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1932 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1933
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1934 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1935 (width and height are doubles)
1936
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1937 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1938 &height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1939
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1940 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1941
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1942 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1943
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1944 height - height of a pixel in physical scale units
1945 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1946
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1947 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1948 info_ptr, &unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1949
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1950 unknowns - array of png_unknown_chunk
1951 structures holding unknown chunks
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1952
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1953 unknowns[i].name - name of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1954
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1955 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1956
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1957 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1958
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1959 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1960
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1961 The value of "i" corresponds to the order in which the
1962 chunks were read from the PNG file or inserted with the
1963 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1964
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1965The data from the pHYs chunk can be retrieved in several convenient
1966forms:
1967
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1968 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1969 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1970
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1971 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1972 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1973
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1974 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1975 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1976
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1977 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1978 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1979
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1980 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1981 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1982
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1983 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1984 info_ptr)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1985
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1986 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1987 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1988
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1989 Each of these returns 0 [signifying "unknown"] if
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1990 the data is not present or if res_x is 0;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]1991 res_x_and_y is 0 if res_x != res_y
1992
1993 Note that because of the way the resolutions are
1994 stored internally, the inch conversions won't
1995 come out to exactly even number. For example,
1996 72 dpi is stored as 0.28346 pixels/meter, and
1997 when this is retrieved it is 71.9988 dpi, so
1998 be sure to round the returned value appropriately
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]1999 if you want to display a reasonable-looking result.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2000
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2001The data from the oFFs chunk can be retrieved in several convenient
2002forms:
2003
2004 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2005
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2006 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2007
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2008 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2009
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2010 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
2011
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2012 Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2013 x and y are 0] if the data is not present or if the
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2014 chunk is present but the unit is the pixel. The
2015 remark about inexact inch conversions applies here
2016 as well, because a value in inches can't always be
2017 converted to microns and back without some loss
2018 of precision.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2019
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2020For more information, see the png_info definition in png.h and the
2021PNG specification for chunk contents. Be careful with trusting
2022rowbytes, as some of the transformations could increase the space
2023needed to hold a row (expand, filler, gray_to_rgb, etc.).
2024See png_read_update_info(), below.
2025
2026A quick word about text_ptr and num_text. PNG stores comments in
2027keyword/text pairs, one pair per chunk, with no limit on the number
2028of text chunks, and a 2^31 byte limit on their size. While there are
2029suggested keywords, there is no requirement to restrict the use to these
2030strings. It is strongly suggested that keywords and text be sensible
2031to humans (that's the point), so don't use abbreviations. Non-printing
2032symbols are not allowed. See the PNG specification for more details.
2033There is also no requirement to have text after the keyword.
2034
2035Keywords should be limited to 79 Latin-1 characters without leading or
2036trailing spaces, but non-consecutive spaces are allowed within the
2037keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2038The text_ptr is an array of png_text structures, each holding a
2039pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2040a text string. The text string, language code, and translated
2041keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2042pairs are put into the array in the order that they are received.
2043However, some or all of the text chunks may be after the image, so, to
2044make sure you have read all the text chunks, don't mess with these
2045until after you read the stuff after the image. This will be
2046mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2047
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2048.SS Input transformations
2049
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2050After you've read the header information, you can set up the library
2051to handle any special transformations of the image data. The various
2052ways to transform the data will be described in the order that they
2053should occur. This is important, as some of these change the color
2054type and/or bit depth of the data, and some others only work on
2055certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2056checks to see if it has data that it can do something with, you should
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2057make sure to only enable a transformation if it will be valid for the
2058data. For example, don't swap red and blue on grayscale data.
2059
2060The colors used for the background and transparency values should be
2061supplied in the same format/depth as the current image data. They
2062are stored in the same format/depth as the image data in a bKGD or tRNS
2063chunk, so this is what libpng expects for this data. The colors are
2064transformed to keep in sync with the image data when an application
2065calls the png_read_update_info() routine (see below).
2066
2067Data will be decoded into the supplied row buffers packed into bytes
2068unless the library has been told to transform it into another format.
2069For example, 4 bit/pixel paletted or grayscale data will be returned
20702 pixels/byte with the leftmost pixel in the high-order bits of the
2071byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2072in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
2073is called to insert filler bytes, either before or after each RGB triplet.
207416-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
2075byte of the color value first, unless png_set_strip_16() is called to
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2076transform it to regular RGB RGB triplets, or png_set_filler() or
2077png_set_add alpha() is called to insert filler bytes, either before or
2078after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
2079be modified with
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2080png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2081
2082The following code transforms grayscale images of less than 8 to 8 bits,
2083changes paletted images to RGB, and adds a full alpha channel if there is
2084transparency information in a tRNS chunk. This is most useful on
2085grayscale images with bit depths of 2 or 4 or if there is a multiple-image
2086viewing application that wishes to treat all images in the same way.
2087
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2088 if (color_type == PNG_COLOR_TYPE_PALETTE)
2089 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2090
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2091 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2092 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
2093
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2094 if (color_type == PNG_COLOR_TYPE_GRAY &&
2095 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
2096
2097The first two functions are actually aliases for png_set_expand(), added
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2098in libpng version 1.0.4, with the function names expanded to improve code
2099readability. In some future version they may actually do different
2100things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2101
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2102As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
2103added. It expands the sample depth without changing tRNS to alpha.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2104
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2105As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2106png_set_expand(), however, the resultant channels have 16 bits rather than 8.
2107Use this when the output color or gray channels are made linear to avoid fairly
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2108severe accuracy loss.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2109
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2110 if (bit_depth < 16)
2111 png_set_expand_16(png_ptr);
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]2112
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2113PNG can have files with 16 bits per channel. If you only can handle
21148 bits per channel, this will strip the pixels down to 8 bit.
2115
2116 if (bit_depth == 16)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2117 png_set_strip_16(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2118
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2119If, for some reason, you don't need the alpha channel on an image,
2120and you want to remove it rather than combining it with the background
2121(but the image author certainly had in mind that you *would* combine
2122it with the background, so that's what you should probably do):
2123
2124 if (color_type & PNG_COLOR_MASK_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2125 png_set_strip_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2126
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2127See below for png_set_background(), which does the correct composition on a
2128single opaque color. This is probably what you should do in all cases rather
2129than use png_set_strip_alpha() - unless you know for sure that it is the wrong
2130thing to do.
2131
2132As of libpng version 1.5.2, almost all useful expansions are supported, the
2133major ommissions are convertion of grayscale to indexed images (which can be
2134done trivially in the application) and convertion of indexed to grayscale (which
2135can be done by a trivial manipulation of the palette.)
2136
2137In the following table, the 01 means grayscale with depth<8, 31 means
2138indexed with depth<8, other numerals represent the color type, "T" means
2139the tRNS chunk is present, A means an alpha channel is present, and O
2140means tRNS or alpha is present but all pixels in the image are opaque.
2141
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2142 FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
John Bowler63d059a2011-02-12 09:03:44 -0600[diff] [blame]2143 TO
2144 01 - [G] - - - - - - - - - - - - -
2145 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q
2146 0 1 G + . . G G G G G G B B GB GB
2147 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt
2148 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt
2149 2 C P C C C + . . C - - CB CB B B
2150 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt
2151 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt
2152 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q
2153 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt
2154 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt
2155 4A lA G A T T GA GT GT GA GT GT + BA G GBA
2156 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G
2157 6A CA PA CA C C A T tT PA P P C CBA + BA
2158 6O CA PBA CA C C A tT T PA P P CBA C BA +
2159
2160Within the matrix,
2161 "+" identifies entries where 'from' and 'to' are the same.
2162 "-" means the transformation is not supported.
2163 "." means nothing is necessary (a tRNS chunk can just be ignored).
2164 "t" means the transformation is obtained by png_set_tRNS.
2165 "A" means the transformation is obtained by png_set_add_alpha().
2166 "X" means the transformation is obtained by png_set_expand().
2167 "1" means the transformation is obtained by
2168 png_set_expand_gray_1_2_4_to_8() (and by png_set_expand() if there
2169 is no transparency in the original or the final format).
2170 "C" means the transformation is obtained by png_set_gray_to_rgb().
2171 "G" means the transformation is obtained by png_set_rgb_to_gray() or
2172 png_set_rgb_to_Y().
2173 "P" means the transformation is obtained by
2174 png_set_expand_palette_to_rgb().
2175 "p" means the transformation is obtained by png_set_packing().
2176 "Q" means the transformation is obtained by png_set_quantize().
2177 "T" means the transformation is obtained by png_set_tRNS_to_alpha().
2178 "B" means the transformation is obtained by png_set_background(), or
2179 png_strip_alpha().
2180 "8" means the transformation is obtained by png_set_strip_16().
2181 "6" means the transformation is obtained by png_set_expand_16().
2182
2183When an entry has multiple transforms listed all are required to cause the
2184right overall transformation. When two transforms are separated by a comma
2185either will do the job. When transforms are enclosed in [] the transform should
2186do the job but this is currently unimplemented - a different format will result
2187if the suggested transformations are used.
2188
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2189In PNG files, the alpha channel in an image
2190is the level of opacity. If you need the alpha channel in an image to
2191be the level of transparency instead of opacity, you can invert the
2192alpha channel (or the tRNS chunk data) after it's read, so that 0 is
2193fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
2194images) is fully transparent, with
2195
2196 png_set_invert_alpha(png_ptr);
2197
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2198PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2199they can, resulting in, for example, 8 pixels per byte for 1 bit
2200files. This code expands to 1 pixel per byte without changing the
2201values of the pixels:
2202
2203 if (bit_depth < 8)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2204 png_set_packing(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2205
2206PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
2207stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2208higher possible bit depth (e.g. from 5 bits/sample in the range [0,31]
2209to 8 bits/sample in the range [0, 255]). However, it is also possible
2210to convert the PNG pixel data back to the original bit depth of the
2211image. This call reduces the pixels back down to the original bit depth:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2212
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2213 png_color_8p sig_bit;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2214
2215 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2216 png_set_shift(png_ptr, sig_bit);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2217
2218PNG files store 3-color pixels in red, green, blue order. This code
2219changes the storage of the pixels to blue, green, red:
2220
2221 if (color_type == PNG_COLOR_TYPE_RGB ||
2222 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2223 png_set_bgr(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2224
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2225PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
2226into 4 or 8 bytes for windowing systems that need them in this format:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2227
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2228 if (color_type == PNG_COLOR_TYPE_RGB)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2229 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2230
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2231where "filler" is the 8 or 16-bit number to fill with, and the location is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2232either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
2233you want the filler before the RGB or after. This transformation
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]2234does not affect images that already have full alpha channels. To add an
2235opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
2236will generate RGBA pixels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2237
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2238Note that png_set_filler() does not change the color type. If you want
2239to do that, you can add a true alpha channel with
2240
2241 if (color_type == PNG_COLOR_TYPE_RGB ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2242 color_type == PNG_COLOR_TYPE_GRAY)
2243 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2244
2245where "filler" contains the alpha value to assign to each pixel.
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]2246This function was added in libpng-1.2.7.
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]2247
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2248If you are reading an image with an alpha channel, and you need the
2249data as ARGB instead of the normal PNG format RGBA:
2250
2251 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2252 png_set_swap_alpha(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2253
2254For some uses, you may want a grayscale image to be represented as
2255RGB. This code will do that conversion:
2256
2257 if (color_type == PNG_COLOR_TYPE_GRAY ||
2258 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2259 png_set_gray_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2260
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2261Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2262with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2263
2264 if (color_type == PNG_COLOR_TYPE_RGB ||
2265 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2266 png_set_rgb_to_gray_fixed(png_ptr, error_action,
2267 int red_weight, int green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2268
2269 error_action = 1: silently do the conversion
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2270
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2271 error_action = 2: issue a warning if the original
2272 image has any pixel where
2273 red != green or red != blue
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2274
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2275 error_action = 3: issue an error and abort the
2276 conversion if the original
2277 image has any pixel where
2278 red != green or red != blue
2279
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2280 red_weight: weight of red component times 100000
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2281
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2282 green_weight: weight of green component times 100000
2283 If either weight is negative, default
2284 weights (21268, 71514) are used.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2285
2286If you have set error_action = 1 or 2, you can
2287later check whether the image really was gray, after processing
2288the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
2289It will return a png_byte that is zero if the image was gray or
22901 if there were any non-gray pixels. bKGD and sBIT data
2291will be silently converted to grayscale, using the green channel
2292data, regardless of the error_action setting.
2293
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2294With red_weight+green_weight<=100000,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2295the normalized graylevel is computed:
2296
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2297 int rw = red_weight * 65536;
2298 int gw = green_weight * 65536;
2299 int bw = 65536 - (rw + gw);
2300 gray = (rw*red + gw*green + bw*blue)/65536;
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2301
2302The default values approximate those recommended in the Charles
2303Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]2304Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2305
2306 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
2307
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2308Libpng approximates this with integers scaled by 32768:
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2309
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2310 Y = (6968 * R + 23434 * G + 2366 * B)/32768
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2311
2312The calculation is done in a linear colorspace, if the image gamma
Glenn Randers-Pehrson9962b842011-01-24 00:12:14 -0600[diff] [blame]2313can be determined.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2314
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]2315If you have a grayscale and you are using png_set_expand_gray_1_2_4_to_8(),
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]2316png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2317a higher bit-depth, you must either supply the background color as a gray
2318value at the original file bit-depth (need_expand = 1) or else supply the
2319background color as an RGB triplet at the final, expanded bit depth
2320(need_expand = 0). Similarly, if you are reading a paletted image, you
2321must either supply the background color as a palette index (need_expand = 1)
2322or as an RGB triplet that may or may not be in the palette (need_expand = 0).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2323
2324 png_color_16 my_background;
2325 png_color_16p image_background;
2326
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2327 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2328 png_set_background(png_ptr, image_background,
2329 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2330 else
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2331 png_set_background(png_ptr, &my_background,
2332 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2333
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2334The png_set_background() function tells libpng to composite images
2335with alpha or simple transparency against the supplied background
2336color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
2337you may use this color, or supply another color more suitable for
2338the current display (e.g., the background color from a web page). You
2339need to tell libpng whether the color is in the gamma space of the
2340display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
2341(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
2342that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
2343know why anyone would use this, but it's here).
2344
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2345To properly display PNG images on any kind of system, the application needs
2346to know what the display gamma is. Ideally, the user will know this, and
2347the application will allow them to set it. One method of allowing the user
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]2348to set the display gamma separately for each system is to check for a
2349SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
2350correctly set.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2351
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]2352Note that display_gamma is the overall gamma correction required to produce
2353pleasing results, which depends on the lighting conditions in the surrounding
2354environment. In a dim or brightly lit room, no compensation other than
2355the physical gamma exponent of the monitor is needed, while in a dark room
2356a slightly smaller exponent is better.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2357
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2358 double gamma, screen_gamma;
2359
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2360 if (/* We have a user-defined screen
2361 gamma value */)
2362 {
2363 screen_gamma = user_defined_screen_gamma;
2364 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2365
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2366 /* One way that applications can share the same
2367 screen gamma value */
2368 else if ((gamma_str = getenv("SCREEN_GAMMA"))
2369 != NULL)
2370 {
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2371 screen_gamma = (double)atof(gamma_str);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2372 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2373
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2374 /* If we don't have another value */
2375 else
2376 {
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2377 screen_gamma = 2.2; /* A good guess for a
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2378 PC monitor in a bright office or a dim room */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2379
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2380 screen_gamma = 2.0; /* A good guess for a
2381 PC monitor in a dark room */
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2382
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2383 screen_gamma = 1.7 or 1.0; /* A good
2384 guess for Mac systems */
2385 }
2386
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]2387The functions png_set_gamma() and its fixed point equivalent
2388png_set_gamma_fixed() handle gamma transformations of the data.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2389Pass both the file gamma and the current screen_gamma. If the file does
2390not have a gamma value, you can pass one anyway if you have an idea what
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2391it is (usually 0.45455 is a good guess for GIF images on PCs). Note
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2392that file gammas are inverted from screen gammas. See the discussions
2393on gamma in the PNG specification for an excellent description of what
2394gamma is, and why all applications should support it. It is strongly
2395recommended that PNG viewers support gamma correction.
2396
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]2397 if (png_get_gAMA(png_ptr, info_ptr, &file_gamma))
2398 png_set_gamma(png_ptr, screen_gamma, file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2399
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2400 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2401 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2402
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2403If you need to reduce an RGB file to a paletted file, or if a paletted
2404file has more entries then will fit on your screen, png_set_quantize()
Glenn Randers-Pehrson862cb202010-04-16 22:12:51 -0500[diff] [blame]2405will do that. Note that this is a simple match quantization that merely
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2406finds the closest color available. This should work fairly well with
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2407optimized palettes, but fairly badly with linear color cubes. If you
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2408pass a palette that is larger then maximum_colors, the file will
2409reduce the number of colors in the palette so it will fit into
2410maximum_colors. If there is a histogram, it will use it to make
2411more intelligent choices when reducing the palette. If there is no
2412histogram, it may not do as good a job.
2413
2414 if (color_type & PNG_COLOR_MASK_COLOR)
2415 {
2416 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2417 PNG_INFO_PLTE))
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2418 {
2419 png_uint_16p histogram = NULL;
2420
2421 png_get_hIST(png_ptr, info_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2422 &histogram);
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2423 png_set_quantize(png_ptr, palette, num_palette,
2424 max_screen_colors, histogram, 1);
2425 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2426
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]2427 else
2428 {
2429 png_color std_color_cube[MAX_SCREEN_COLORS] =
2430 { ... colors ... };
2431
2432 png_set_quantize(png_ptr, std_color_cube,
2433 MAX_SCREEN_COLORS, MAX_SCREEN_COLORS,
2434 NULL,0);
2435 }
2436 }
2437
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2438PNG files describe monochrome as black being zero and white being one.
2439The following code will reverse this (make black be one and white be
2440zero):
2441
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]2442 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
2443 png_set_invert_mono(png_ptr);
2444
2445This function can also be used to invert grayscale and gray-alpha images:
2446
2447 if (color_type == PNG_COLOR_TYPE_GRAY ||
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2448 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2449 png_set_invert_mono(png_ptr);
2450
2451PNG files store 16 bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2452ie. most significant bits first). This code changes the storage to the
2453other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2454way PCs store them):
2455
2456 if (bit_depth == 16)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2457 png_set_swap(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2458
2459If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
2460need to change the order the pixels are packed into bytes, you can use:
2461
2462 if (bit_depth < 8)
2463 png_set_packswap(png_ptr);
2464
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2465Finally, you can write your own transformation function if none of
2466the existing ones meets your needs. This is done by setting a callback
2467with
2468
2469 png_set_read_user_transform_fn(png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2470 read_transform_fn);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2471
2472You must supply the function
2473
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]2474 void read_transform_fn(png_structp png_ptr, png_row_infop
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2475 row_info, png_bytep data)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2476
2477See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2478after all of the other transformations have been processed. Take care with
2479interlaced images if you do the interlace yourself - the width of the row is the
2480width in 'row_info', not the overall image width.
2481
2482If supported libpng provides two information routines that you can use to find
2483where you are in processing the image:
2484
2485 png_get_current_pass_number(png_structp png_ptr);
2486 png_get_current_row_number(png_structp png_ptr);
2487
2488Don't try using these outside a transform callback - firstly they are only
2489supported if user transforms are supported, secondly they may well return
2490unexpected results unless the row is actually being processed at the moment they
2491are called.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2492
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame^]2493With interlaced
2494images the value returned is the row in the input sub-image image. Use
2495PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
2496find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
2497
2498The discussion of interlace handling above contains more information on how to
2499use these values.
2500
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2501You can also set up a pointer to a user structure for use by your
2502callback function, and you can inform libpng that your transform
2503function will change the number of channels or bit depth with the
2504function
2505
2506 png_set_user_transform_info(png_ptr, user_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2507 user_depth, user_channels);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2508
2509The user's application, not libpng, is responsible for allocating and
2510freeing any memory required for the user structure.
2511
2512You can retrieve the pointer via the function
2513png_get_user_transform_ptr(). For example:
2514
2515 voidp read_user_transform_ptr =
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2516 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2517
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2518The last thing to handle is interlacing; this is covered in detail below,
2519but you must call the function here if you want libpng to handle expansion
2520of the interlaced image.
2521
2522 number_of_passes = png_set_interlace_handling(png_ptr);
2523
2524After setting the transformations, libpng can update your png_info
2525structure to reflect any transformations you've requested with this
2526call. This is most useful to update the info structure's rowbytes
2527field so you can use it to allocate your image memory. This function
2528will also update your palette with the correct screen_gamma and
2529background if these have been given with the calls above.
2530
2531 png_read_update_info(png_ptr, info_ptr);
2532
2533After you call png_read_update_info(), you can allocate any
2534memory you need to hold the image. The row data is simply
2535raw byte data for all forms of images. As the actual allocation
2536varies among applications, no example will be given. If you
2537are allocating one large chunk, you will need to build an
2538array of pointers to each row, as it will be needed for some
2539of the functions below.
2540
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2541Remember: Before you call png_read_update_info(), the png_get_
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2542functions return the values corresponding to the original PNG image.
2543After you call png_read_update_info the values refer to the image
2544that libpng will output. Consequently you must call all the png_set_
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2545functions before you call png_read_update_info(). This is particularly
2546important for png_set_interlace_handling() - if you are going to call
2547png_read_update_info() you must call png_set_interlace_handling() before
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2548it unless you want to receive interlaced output.
2549
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2550.SS Reading image data
2551
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2552After you've allocated memory, you can read the image data.
2553The simplest way to do this is in one function call. If you are
2554allocating enough memory to hold the whole image, you can just
2555call png_read_image() and libpng will read in all the image data
2556and put it in the memory area supplied. You will need to pass in
2557an array of pointers to each row.
2558
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]2559This function automatically handles interlacing, so you don't
2560need to call png_set_interlace_handling() (unless you call
2561png_read_update_info()) or call this function multiple times, or any
2562of that other stuff necessary with png_read_rows().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2563
2564 png_read_image(png_ptr, row_pointers);
2565
2566where row_pointers is:
2567
2568 png_bytep row_pointers[height];
2569
2570You can point to void or char or whatever you use for pixels.
2571
2572If you don't want to read in the whole image at once, you can
2573use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2574interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2575
2576 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2577 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2578
2579where row_pointers is the same as in the png_read_image() call.
2580
2581If you are doing this just one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2582a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2583
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2584 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2585 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2586
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2587If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
2588get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2589interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7);
2590a somewhat complicated 2D interlace scheme, known as Adam7, that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2591breaks down an image into seven smaller images of varying size, based
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2592on an 8x8 grid. This number is defined (from libpng 1.5) as
2593PNG_INTERLACE_ADAM7_PASSES in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2594
2595libpng can fill out those images or it can give them to you "as is".
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2596It is almost always better to have libpng handle the interlacing for you.
2597If you want the images filled out, there are two ways to do that. The one
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2598mentioned in the PNG specification is to expand each pixel to cover
2599those pixels that have not been read yet (the "rectangle" method).
2600This results in a blocky image for the first pass, which gradually
2601smooths out as more pixels are read. The other method is the "sparkle"
2602method, where pixels are drawn only in their final locations, with the
2603rest of the image remaining whatever colors they were initialized to
2604before the start of the read. The first method usually looks better,
2605but tends to be slower, as there are more pixels to put in the rows.
2606
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2607If, as is likely, you want libpng to expand the images, call this before
2608calling png_start_read_image() or png_read_update_info():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2609
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2610 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2611 number_of_passes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2612 = png_set_interlace_handling(png_ptr);
2613
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2614This will return the number of passes needed. Currently, this is seven,
2615but may change if another interlace type is added. This function can be
2616called even if the file is not interlaced, where it will return one pass.
2617You then need to read the whole image 'number_of_passes' times. Each time
2618will distribute the pixels from the current pass to the correct place in
2619the output image, so you need to supply the same rows to png_read_rows in
2620each pass.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]2621
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2622If you are not going to display the image after each pass, but are
2623going to wait until the entire image is read in, use the sparkle
2624effect. This effect is faster and the end result of either method
2625is exactly the same. If you are planning on displaying the image
2626after each pass, the "rectangle" effect is generally considered the
2627better looking one.
2628
2629If you only want the "sparkle" effect, just call png_read_rows() as
2630normal, with the third parameter NULL. Make sure you make pass over
2631the image number_of_passes times, and you don't change the data in the
2632rows between calls. You can change the locations of the data, just
2633not the data. Each pass only writes the pixels appropriate for that
2634pass, and assumes the data from previous passes is still valid.
2635
2636 png_read_rows(png_ptr, row_pointers, NULL,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2637 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2638
2639If you only want the first effect (the rectangles), do the same as
2640before except pass the row buffer in the third parameter, and leave
2641the second parameter NULL.
2642
2643 png_read_rows(png_ptr, NULL, row_pointers,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2644 number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2645
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2646If you don't want libpng to handle the interlacing details, just call
2647png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images.
2648Each of the images is a valid image by itself, however you will almost
2649certainly need to distribute the pixels from each sub-image to the
2650correct place. This is where everything gets very tricky.
2651
2652If you want to retrieve the separate images you must pass the correct
2653number of rows to each successive call of png_read_rows(). The calculation
2654gets pretty complicated for small images, where some sub-images may
2655not even exist because either their width or height ends up zero.
2656libpng provides two macros to help you in 1.5 and later versions:
2657
2658 png_uint_32 width = PNG_PASS_COLS(image_width, pass_number);
2659 png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number);
2660
2661Respectively these tell you the width and height of the sub-image
2662corresponding to the numbered pass. 'pass' is in in the range 0 to 6 -
2663this can be confusing because the specification refers to the same passes
2664as 1 to 7! Be careful, you must check both the width and height before
2665calling png_read_rows() and not call it for that pass if either is zero.
2666
2667You can, of course, read each sub-image row by row. If you want to
2668produce optimal code to make a pixel-by-pixel transformation of an
2669interlaced image this is the best approach; read each row of each pass,
2670transform it, and write it out to a new interlaced image.
2671
2672If you want to de-interlace the image yourself libpng provides further
2673macros to help that tell you where to place the pixels in the output image.
2674Because the interlacing scheme is rectangular - sub-image pixels are always
2675arranged on a rectangular grid - all you need to know for each pass is the
2676starting column and row in the output image of the first pixel plus the
2677spacing between each pixel. As of libpng 1.5 there are four macros to
2678retrieve this information:
2679
2680 png_uint_32 x = PNG_PASS_START_COL(pass);
2681 png_uint_32 y = PNG_PASS_START_ROW(pass);
2682 png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass);
2683 png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass);
2684
2685These allow you to write the obvious loop:
2686
2687 png_uint_32 input_y = 0;
2688 png_uint_32 output_y = PNG_PASS_START_ROW(pass);
2689
2690 while (output_y < output_image_height)
2691 {
2692 png_uint_32 input_x = 0;
2693 png_uint_32 output_x = PNG_PASS_START_COL(pass);
2694
2695 while (output_x < output_image_width)
2696 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2697 image[output_y][output_x] =
2698 subimage[pass][input_y][input_x++];
2699
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2700 output_x += xStep;
2701 }
2702
2703 ++input_y;
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2704 output_y += yStep;
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2705 }
2706
2707Notice that the steps between successive output rows and columns are
2708returned as shifts. This is possible because the pixels in the subimages
2709are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original
2710image. In practice you may need to directly calculate the output coordinate
2711given an input coordinate. libpng provides two further macros for this
2712purpose:
2713
2714 png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass);
2715 png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass);
2716
2717Finally a pair of macros are provided to tell you if a particular image
2718row or column appears in a given pass:
2719
2720 int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass);
2721 int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass);
2722
2723Bear in mind that you will probably also need to check the width and height
2724of the pass in addition to the above to be sure the pass even exists!
2725
2726With any luck you are convinced by now that you don't want to do your own
2727interlace handling. In reality normally the only good reason for doing this
2728is if you are processing PNG files on a pixel-by-pixel basis and don't want
2729to load the whole file into memory when it is interlaced.
2730
2731libpng includes a test program, pngvalid, that illustrates reading and
2732writing of interlaced images. If you can't get interlacing to work in your
2733code and don't want to leave it to libpng (the recommended approach) see
2734how pngvalid.c does it.
2735
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2736.SS Finishing a sequential read
2737
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]2738After you are finished reading the image through the
2739low-level interface, you can finish reading the file. If you are
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2740interested in comments or time, which may be stored either before or
2741after the image data, you should pass the separate png_info struct if
2742you want to keep the comments from before and after the image
2743separate. If you are not interested, you can pass NULL.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2744
2745 png_read_end(png_ptr, end_info);
2746
2747When you are done, you can free all memory allocated by libpng like this:
2748
2749 png_destroy_read_struct(&png_ptr, &info_ptr,
2750 &end_info);
2751
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2752It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2753point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2754
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2755 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2756
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2757 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2758 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2759 more of
2760 PNG_FREE_PLTE, PNG_FREE_TRNS,
2761 PNG_FREE_HIST, PNG_FREE_ICCP,
2762 PNG_FREE_PCAL, PNG_FREE_ROWS,
2763 PNG_FREE_SCAL, PNG_FREE_SPLT,
2764 PNG_FREE_TEXT, PNG_FREE_UNKN,
2765 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2766
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2767 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2768 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2769
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2770This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2771already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2772by the user and not by libpng, and will in those cases do nothing.
2773The "seq" parameter is ignored if only one item of the selected data
2774type, such as PLTE, is allowed. If "seq" is not -1, and multiple items
2775are allowed for the data type identified in the mask, such as text or
2776sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2777
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2778The default behavior is only to free data that was allocated internally
2779by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2780or so that it will free data that was allocated by the user with png_malloc()
2781or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2782
2783 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2784
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2785 freer - one of
2786 PNG_DESTROY_WILL_FREE_DATA
2787 PNG_SET_WILL_FREE_DATA
2788 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2789
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2790 mask - which data elements are affected
2791 same choices as in png_free_data()
2792
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2793This function only affects data that has already been allocated.
2794You can call this function after reading the PNG data but before calling
2795any png_set_*() functions, to control whether the user or the png_set_*()
2796function is responsible for freeing any existing data that might be present,
2797and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2798or png_destroy_*() is supposed to free the data. When the user assumes
2799responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2800png_free() to free it, and when the user transfers responsibility to libpng
2801for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]2802or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2803
2804If you allocated your row_pointers in a single block, as suggested above in
2805the description of the high level read interface, you must not transfer
2806responsibility for freeing it to the png_set_rows or png_read_destroy function,
2807because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2808
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2809If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2810separately, do not transfer responsibility for freeing text_ptr to libpng,
2811because when libpng fills a png_text structure it combines these members with
2812the key member, and png_free_data() will free only text_ptr.key. Similarly,
2813if you transfer responsibility for free'ing text_ptr from libpng to your
2814application, your application must not separately free those members.
2815
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2816The png_free_data() function will turn off the "valid" flag for anything
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]2817it frees. If you need to turn the flag off for a chunk that was freed by
2818your application instead of by libpng, you can use
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2819
2820 png_set_invalid(png_ptr, info_ptr, mask);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2821
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2822 mask - identifies the chunks to be made invalid,
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2823 containing the bitwise OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2824 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2825 PNG_INFO_gAMA, PNG_INFO_sBIT,
2826 PNG_INFO_cHRM, PNG_INFO_PLTE,
2827 PNG_INFO_tRNS, PNG_INFO_bKGD,
2828 PNG_INFO_hIST, PNG_INFO_pHYs,
2829 PNG_INFO_oFFs, PNG_INFO_tIME,
2830 PNG_INFO_pCAL, PNG_INFO_sRGB,
2831 PNG_INFO_iCCP, PNG_INFO_sPLT,
2832 PNG_INFO_sCAL, PNG_INFO_IDAT
2833
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2834For a more compact example of reading a PNG image, see the file example.c.
2835
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2836.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2837
2838The progressive reader is slightly different then the non-progressive
2839reader. Instead of calling png_read_info(), png_read_rows(), and
2840png_read_end(), you make one call to png_process_data(), which calls
2841callbacks when it has the info, a row, or the end of the image. You
2842set up these callbacks with png_set_progressive_read_fn(). You don't
2843have to worry about the input/output functions of libpng, as you are
2844giving the library the data directly in png_process_data(). I will
2845assume that you have read the section on reading PNG files above,
2846so I will only highlight the differences (although I will show
2847all of the code).
2848
2849png_structp png_ptr;
2850png_infop info_ptr;
2851
2852 /* An example code fragment of how you would
2853 initialize the progressive reader in your
2854 application. */
2855 int
2856 initialize_png_reader()
2857 {
2858 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2859 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2860 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2861
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2862 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2863 return (ERROR);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2864
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2865 info_ptr = png_create_info_struct(png_ptr);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2866
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2867 if (!info_ptr)
2868 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2869 png_destroy_read_struct(&png_ptr,
2870 (png_infopp)NULL, (png_infopp)NULL);
2871 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2872 }
2873
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2874 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2875 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2876 png_destroy_read_struct(&png_ptr, &info_ptr,
2877 (png_infopp)NULL);
2878 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2879 }
2880
2881 /* This one's new. You can provide functions
2882 to be called when the header info is valid,
2883 when each row is completed, and when the image
2884 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2885 you can specify NULL parameters. Even when all
2886 three functions are NULL, you need to call
2887 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2888 any struct as the user_ptr (cast to a void pointer
2889 for the function call), and retrieve the pointer
2890 from inside the callbacks using the function
2891
2892 png_get_progressive_ptr(png_ptr);
2893
2894 which will return a void pointer, which you have
2895 to cast appropriately.
2896 */
2897 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2898 info_callback, row_callback, end_callback);
2899
2900 return 0;
2901 }
2902
2903 /* A code fragment that you call as you receive blocks
2904 of data */
2905 int
2906 process_data(png_bytep buffer, png_uint_32 length)
2907 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2908 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2909 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2910 png_destroy_read_struct(&png_ptr, &info_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2911 (png_infopp)NULL);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]2912 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2913 }
2914
2915 /* This one's new also. Simply give it a chunk
2916 of data from the file stream (in order, of
2917 course). On machines with segmented memory
2918 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2919 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2920 of 4K. Although you can give it much less if
2921 necessary (I assume you can give it chunks of
2922 1 byte, I haven't tried less then 256 bytes
2923 yet). When this function returns, you may
2924 want to display any rows that were generated
2925 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2926 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2927 */
2928 png_process_data(png_ptr, info_ptr, buffer, length);
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2929
2930 /* At this point you can call png_process_data_skip if
2931 you want to handle data the library will skip yourself;
2932 it simply returns the number of bytes to skip (and stops
2933 libpng skipping that number of bytes on the next
2934 png_process_data call).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2935 return 0;
2936 }
2937
2938 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2939 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2940 has been supplied so all of the header has been
2941 read.
2942 */
2943 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2944 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2945 {
2946 /* Do any setup here, including setting any of
2947 the transformations mentioned in the Reading
2948 PNG files section. For now, you _must_ call
2949 either png_start_read_image() or
2950 png_read_update_info() after all the
2951 transformations are set (even if you don't set
2952 any). You may start getting rows before
2953 png_process_data() returns, so this is your
2954 last chance to prepare for that.
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2955
2956 This is where you turn on interlace handling,
2957 assuming you don't want to do it yourself.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]2958
2959 If you need to you can stop the processing of
2960 your original input data at this point by calling
2961 png_process_data_pause. This returns the number
2962 of unprocessed bytes from the last png_process_data
2963 call - it is up to you to ensure that the next call
2964 sees these bytes again. If you don't want to bother
2965 with this you can get libpng to cache the unread
2966 bytes by setting the 'save' parameter (see png.h) but
2967 then libpng will have to copy the data internally.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2968 */
2969 }
2970
2971 /* This function is called when each row of image
2972 data is complete */
2973 void
2974 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2975 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2976 {
2977 /* If the image is interlaced, and you turned
2978 on the interlace handler, this function will
2979 be called for every row in every pass. Some
2980 of these rows will not be changed from the
2981 previous pass. When the row is not changed,
2982 the new_row variable will be NULL. The rows
2983 and passes are called in order, so you don't
2984 really need the row_num and pass, but I'm
2985 supplying them because it may make your life
2986 easier.
2987
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]2988 If you did not turn on interlace handling then
2989 the callback is called for each row of each
2990 sub-image when the image is interlaced. In this
2991 case 'row_num' is the row in the sub-image, not
2992 the row in the output image as it is in all other
2993 cases.
2994
2995 For the non-NULL rows of interlaced images when
2996 you have switched on libpng interlace handling,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2997 you must call png_progressive_combine_row()
2998 passing in the row and the old row. You can
2999 call this function for NULL rows (it will just
3000 return) and for non-interlaced images (it just
3001 does the memcpy for you) if it will make the
3002 code easier. Thus, you can just do this for
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3003 all cases if you switch on interlace handling;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3004 */
3005
3006 png_progressive_combine_row(png_ptr, old_row,
3007 new_row);
3008
3009 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]3010 previously for the row. Note that the first
3011 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3012 the old row, so the rows do not have to be
3013 initialized. After the first pass (and only
3014 for interlaced images), you will have to pass
3015 the current row, and the function will combine
3016 the old row and the new row.
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3017
3018 You can also call png_process_data_pause in this
3019 callback - see above.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3020 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3021 }
3022
3023 void
3024 end_callback(png_structp png_ptr, png_infop info)
3025 {
3026 /* This function is called after the whole image
3027 has been read, including any chunks after the
3028 image (up to and including the IEND). You
3029 will usually have the same info chunk as you
3030 had in the header, although some data may have
3031 been added to the comments and time fields.
3032
3033 Most people won't do much here, perhaps setting
3034 a flag that marks the image as finished.
3035 */
3036 }
3037
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3038
3039
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3040.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3041
3042Much of this is very similar to reading. However, everything of
3043importance is repeated here, so you won't have to constantly look
3044back up in the reading section to understand writing.
3045
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3046.SS Setup
3047
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3048You will want to do the I/O initialization before you get into libpng,
3049so if it doesn't work, you don't have anything to undo. If you are not
3050using the standard I/O functions, you will need to replace them with
3051custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3052
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3053 FILE *fp = fopen(file_name, "wb");
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3054
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3055 if (!fp)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3056 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3057
3058Next, png_struct and png_info need to be allocated and initialized.
3059As these can be both relatively large, you may not want to store these
3060on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3061will want to check if they return NULL. If you are also reading,
3062you won't want to name your read structure and your write structure
3063both "png_ptr"; you can call them anything you like, such as
3064"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3065
3066 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3067 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3068 user_error_fn, user_warning_fn);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3069
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3070 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3071 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3072
3073 png_infop info_ptr = png_create_info_struct(png_ptr);
3074 if (!info_ptr)
3075 {
3076 png_destroy_write_struct(&png_ptr,
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3077 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3078 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3079 }
3080
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3081If you want to use your own memory allocation routines,
3082define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3083png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3084
3085 png_structp png_ptr = png_create_write_struct_2
3086 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
3087 user_error_fn, user_warning_fn, (png_voidp)
3088 user_mem_ptr, user_malloc_fn, user_free_fn);
3089
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3090After you have these structures, you will need to set up the
3091error handling. When libpng encounters an error, it expects to
3092longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3093setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3094write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3095the png_jmpbuf(png_ptr) every time you enter a new routine that will
3096call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3097for your compiler for more information on setjmp/longjmp. See
3098the discussion on libpng error handling in the Customizing Libpng
3099section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3100
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3101 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3102 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3103 png_destroy_write_struct(&png_ptr, &info_ptr);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]3104 fclose(fp);
3105 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3106 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3107 ...
3108 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3109
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3110If you would rather avoid the complexity of setjmp/longjmp issues,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3111you can compile libpng with PNG_NO_SETJMP, in which case
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3112errors will result in a call to PNG_ABORT() which defaults to abort().
3113
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]3114You can #define PNG_ABORT() to a function that does something
3115more useful than abort(), as long as your function does not
3116return.
3117
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3118Now you need to set up the output code. The default for libpng is to
3119use the C function fwrite(). If you use this, you will need to pass a
3120valid FILE * in the function png_init_io(). Be sure that the file is
3121opened in binary mode. Again, if you wish to handle writing data in
3122another way, see the discussion on libpng I/O handling in the Customizing
3123Libpng section below.
3124
3125 png_init_io(png_ptr, fp);
3126
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]3127If you are embedding your PNG into a datastream such as MNG, and don't
3128want libpng to write the 8-byte signature, or if you have already
3129written the signature in your application, use
3130
3131 png_set_sig_bytes(png_ptr, 8);
3132
3133to inform libpng that it should not write a signature.
3134
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3135.SS Write callbacks
3136
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3137At this point, you can set up a callback function that will be
3138called after each row has been written, which you can use to control
3139a progress meter or the like. It's demonstrated in pngtest.c.
3140You must supply a function
3141
Glenn Randers-Pehrson81ce8892011-01-24 08:04:37 -0600[diff] [blame]3142 void write_row_callback(png_structp png_ptr, png_uint_32 row,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3143 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3144 {
3145 /* put your code here */
3146 }
3147
3148(You can give it another name that you like instead of "write_row_callback")
3149
3150To inform libpng about your function, use
3151
3152 png_set_write_status_fn(png_ptr, write_row_callback);
3153
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3154You now have the option of modifying how the compression library will
3155run. The following functions are mainly for testing, but may be useful
3156in some cases, like if you need to write PNG files extremely fast and
3157are willing to give up some compression, or if you want to get the
3158maximum possible compression at the expense of slower writing. If you
3159have no special needs in this area, let the library do what it wants by
3160not calling this function at all, as it has been tuned to deliver a good
3161speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3162the filter method, for which the only valid values are 0 (as of the
3163July 1999 PNG specification, version 1.2) or 64 (if you are writing
3164a PNG datastream that is to be embedded in a MNG datastream). The third
3165parameter is a flag that indicates which filter type(s) are to be tested
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3166for each scanline. See the PNG specification for details on the specific
3167filter types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3168
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3169
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3170 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3171 specific filters. You can use either a single
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3172 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3173 or more PNG_FILTER_NAME masks.
3174 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3175 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3176 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
3177 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
3178 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3179 PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3180 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
3181 PNG_ALL_FILTERS);
3182
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3183If an application wants to start and stop using particular filters during
3184compression, it should start out with all of the filters (to ensure that
3185the previous row of pixels will be stored in case it's needed later),
3186and then add and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3187
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3188If you are writing a PNG datastream that is to be embedded in a MNG
3189datastream, the second parameter can be either 0 or 64.
3190
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3191The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3192library, and should mostly be ignored unless you really know what you are
3193doing. The only generally useful call is png_set_compression_level()
3194which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3195data. See the Compression Library (zlib.h and algorithm.txt, distributed
3196with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3197
3198 /* set the zlib compression level */
3199 png_set_compression_level(png_ptr,
3200 Z_BEST_COMPRESSION);
3201
3202 /* set other zlib parameters */
3203 png_set_compression_mem_level(png_ptr, 8);
3204 png_set_compression_strategy(png_ptr,
3205 Z_DEFAULT_STRATEGY);
3206 png_set_compression_window_bits(png_ptr, 15);
3207 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3208 png_set_compression_buffer_size(png_ptr, 8192)
3209
3210extern PNG_EXPORT(void,png_set_zbuf_size)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3211
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3212.SS Setting the contents of info for output
3213
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3214You now need to fill in the png_info structure with all the data you
3215wish to write before the actual image. Note that the only thing you
3216are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3217chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3218the latest PNG specification for more information on that. If you
3219wish to write them before the image, fill them in now, and flag that
3220data as being valid. If you want to wait until after the data, don't
3221fill them until png_write_end(). For all the fields in png_info and
3222their data types, see png.h. For explanations of what the fields
3223contain, see the PNG specification.
3224
3225Some of the more important parts of the png_info are:
3226
3227 png_set_IHDR(png_ptr, info_ptr, width, height,
3228 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3229 compression_type, filter_method)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3230
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3231 width - holds the width of the image
3232 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3233
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3234 height - holds the height of the image
3235 in pixels (up to 2^31).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3236
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3237 bit_depth - holds the bit depth of one of the
3238 image channels.
3239 (valid values are 1, 2, 4, 8, 16
3240 and depend also on the
3241 color_type. See also significant
3242 bits (sBIT) below).
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3243
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3244 color_type - describes which color/alpha
3245 channels are present.
3246 PNG_COLOR_TYPE_GRAY
3247 (bit depths 1, 2, 4, 8, 16)
3248 PNG_COLOR_TYPE_GRAY_ALPHA
3249 (bit depths 8, 16)
3250 PNG_COLOR_TYPE_PALETTE
3251 (bit depths 1, 2, 4, 8)
3252 PNG_COLOR_TYPE_RGB
3253 (bit_depths 8, 16)
3254 PNG_COLOR_TYPE_RGB_ALPHA
3255 (bit_depths 8, 16)
3256
3257 PNG_COLOR_MASK_PALETTE
3258 PNG_COLOR_MASK_COLOR
3259 PNG_COLOR_MASK_ALPHA
3260
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3261 interlace_type - PNG_INTERLACE_NONE or
3262 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3263
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3264 compression_type - (must be
3265 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3266
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3267 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
3268 or, if you are writing a PNG to
3269 be embedded in a MNG datastream,
3270 can also be
3271 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3272
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3273If you call png_set_IHDR(), the call must appear before any of the
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]3274other png_set_*() functions, because they might require access to some of
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3275the IHDR settings. The remaining png_set_*() functions can be called
3276in any order.
3277
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3278If you wish, you can reset the compression_type, interlace_type, or
3279filter_method later by calling png_set_IHDR() again; if you do this, the
3280width, height, bit_depth, and color_type must be the same in each call.
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3281
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3282 png_set_PLTE(png_ptr, info_ptr, palette,
3283 num_palette);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3284
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3285 palette - the palette for the file
3286 (array of png_color)
3287 num_palette - number of entries in the palette
3288
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3289 png_set_gAMA(png_ptr, info_ptr, file_gamma);
3290 png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3291
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3292 file_gamma - the gamma at which the image was
3293 created (PNG_INFO_gAMA)
3294
3295 int_file_gamma - 100,000 times the gamma at which
3296 the image was created
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3297
3298 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3299
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3300 srgb_intent - the rendering intent
3301 (PNG_INFO_sRGB) The presence of
3302 the sRGB chunk means that the pixel
3303 data is in the sRGB color space.
3304 This chunk also implies specific
3305 values of gAMA and cHRM. Rendering
3306 intent is the CSS-1 property that
3307 has been defined by the International
3308 Color Consortium
3309 (http://www.color.org).
3310 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3311 PNG_sRGB_INTENT_SATURATION,
3312 PNG_sRGB_INTENT_PERCEPTUAL,
3313 PNG_sRGB_INTENT_ABSOLUTE, or
3314 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3315
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3316
3317 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
3318 srgb_intent);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3319
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3320 srgb_intent - the rendering intent
3321 (PNG_INFO_sRGB) The presence of the
3322 sRGB chunk means that the pixel
3323 data is in the sRGB color space.
3324 This function also causes gAMA and
3325 cHRM chunks with the specific values
3326 that are consistent with sRGB to be
3327 written.
3328
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3329 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3330 profile, proflen);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3331
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3332 name - The profile name.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3333
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3334 compression_type - The compression type; always
3335 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
3336 You may give NULL to this argument to
3337 ignore it.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3338
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3339 profile - International Color Consortium color
3340 profile data. May contain NULs.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3341
Glenn Randers-Pehrson4a5a1ec2011-01-15 11:43:28 -0600[diff] [blame]3342 proflen - length of profile data in bytes.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3343
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3344 png_set_sBIT(png_ptr, info_ptr, sig_bit);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3345
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3346 sig_bit - the number of significant bits for
3347 (PNG_INFO_sBIT) each of the gray, red,
3348 green, and blue channels, whichever are
3349 appropriate for the given color type
3350 (png_color_16)
3351
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3352 png_set_tRNS(png_ptr, info_ptr, trans_alpha,
3353 num_trans, trans_color);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3354
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3355 trans_alpha - array of alpha (transparency)
3356 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3357
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3358 trans_color - graylevel or color sample values
3359 (in order red, green, blue) of the
3360 single transparent color for
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]3361 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3362
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3363 num_trans - number of transparent entries
3364 (PNG_INFO_tRNS)
3365
3366 png_set_hIST(png_ptr, info_ptr, hist);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3367
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3368 hist - histogram of palette (array of
Glenn Randers-Pehrson8d0bc0f2011-01-25 22:15:58 -0600[diff] [blame]3369 png_uint_16) (PNG_INFO_hIST)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3370
3371 png_set_tIME(png_ptr, info_ptr, mod_time);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3372
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3373 mod_time - time image was last modified
3374 (PNG_VALID_tIME)
3375
3376 png_set_bKGD(png_ptr, info_ptr, background);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3377
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3378 background - background color (PNG_VALID_bKGD)
3379
3380 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3381
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3382 text_ptr - array of png_text holding image
3383 comments
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3384
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3385 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3386 on "text" PNG_TEXT_COMPRESSION_NONE
3387 PNG_TEXT_COMPRESSION_zTXt
3388 PNG_ITXT_COMPRESSION_NONE
3389 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3390 text_ptr[i].key - keyword for comment. Must contain
3391 1-79 characters.
3392 text_ptr[i].text - text comments for current
3393 keyword. Can be NULL or empty.
3394 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3395 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3396 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3397 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3398 text_ptr[i].lang - language of comment (NULL or
3399 empty for unknown).
3400 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
3401 or empty for unknown).
Glenn Randers-Pehrson8f5846f2009-10-31 21:31:08 -0500[diff] [blame]3402 Note that the itxt_length, lang, and lang_key
3403 members of the text_ptr structure only exist
3404 when the library is built with iTXt chunk support.
3405
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3406 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3407
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3408 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
3409 num_spalettes);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3410
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3411 palette_ptr - array of png_sPLT_struct structures
3412 to be added to the list of palettes
3413 in the info structure.
3414 num_spalettes - number of palette structures to be
3415 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3416
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3417 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
3418 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3419
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3420 offset_x - positive offset from the left
3421 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3422
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3423 offset_y - positive offset from the top
3424 edge of the screen
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3425
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3426 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
3427
3428 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
3429 unit_type);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3430
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3431 res_x - pixels/unit physical resolution
3432 in x direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3433
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3434 res_y - pixels/unit physical resolution
3435 in y direction
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3436
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3437 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3438 PNG_RESOLUTION_METER
3439
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3440 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3441
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3442 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3443
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3444 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3445
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3446 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3447 (width and height are doubles)
3448
3449 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3450
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3451 unit - physical scale units (an integer)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3452
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3453 width - width of a pixel in physical scale units
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3454
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3455 height - height of a pixel in physical scale units
3456 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3457
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3458 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
3459 num_unknowns)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3460
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3461 unknowns - array of png_unknown_chunk
3462 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3463 unknowns[i].name - name of unknown chunk
3464 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]3465 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3466 unknowns[i].location - position to write chunk in file
3467 0: do not write chunk
3468 PNG_HAVE_IHDR: before PLTE
3469 PNG_HAVE_PLTE: before IDAT
3470 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3471
3472The "location" member is set automatically according to
3473what part of the output file has already been written.
3474You can change its value after calling png_set_unknown_chunks()
3475as demonstrated in pngtest.c. Within each of the "locations",
3476the chunks are sequenced according to their position in the
3477structure (that is, the value of "i", which is the order in which
3478the chunk was either read from the input file or defined with
3479png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3480
3481A quick word about text and num_text. text is an array of png_text
3482structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3483Each png_text structure holds a language code, a keyword, a text value,
3484and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3485
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3486The compression types have the same valid numbers as the compression
3487types of the image data. Currently, the only valid number is zero.
3488However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3489images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3490text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3491Because tEXt and zTXt chunks don't have a language field, if you
3492specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
3493any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3494
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3495Until text gets around 1000 bytes, it is not worth compressing it.
3496After the text has been written out to the file, the compression type
3497is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
3498so that it isn't written out again at the end (in case you are calling
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3499png_write_end() with the same struct).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3500
3501The keywords that are given in the PNG Specification are:
3502
3503 Title Short (one line) title or
3504 caption for image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3505
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3506 Author Name of image's creator
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3507
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3508 Description Description of image (possibly long)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3509
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3510 Copyright Copyright notice
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3511
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3512 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3513 (usually RFC 1123 format, see below)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3514
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3515 Software Software used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3516
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3517 Disclaimer Legal disclaimer
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3518
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3519 Warning Warning of nature of content
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3520
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3521 Source Device used to create the image
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3522
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3523 Comment Miscellaneous comment; conversion
3524 from other image format
3525
3526The keyword-text pairs work like this. Keywords should be short
3527simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3528keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3529on keywords. You can repeat keywords in a file. You can even write
3530some text before the image and some after. For example, you may want
3531to put a description of the image before the image, but leave the
3532disclaimer until after, so viewers working over modem connections
3533don't have to wait for the disclaimer to go over the modem before
3534they start seeing the image. Finally, keywords should be full
3535words, not abbreviations. Keywords and text are in the ISO 8859-1
3536(Latin-1) character set (a superset of regular ASCII) and can not
3537contain NUL characters, and should not contain control or other
3538unprintable characters. To make the comments widely readable, stick
3539with basic ASCII, and avoid machine specific character set extensions
3540like the IBM-PC character set. The keyword must be present, but
3541you can leave off the text string on non-compressed pairs.
3542Compressed pairs must have a text string, as only the text string
3543is compressed anyway, so the compression would be meaningless.
3544
3545PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3546conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3547time_t and png_convert_from_struct_tm() for struct tm. The
3548time_t routine uses gmtime(). You don't have to use either of
3549these, but if you wish to fill in the png_time structure directly,
3550you should provide the time in universal time (GMT) if possible
3551instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3552year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3553that months start with 1.
3554
3555If you want to store the time of the original image creation, you should
3556use a plain tEXt chunk with the "Creation Time" keyword. This is
3557necessary because the "creation time" of a PNG image is somewhat vague,
3558depending on whether you mean the PNG file, the time the image was
3559created in a non-PNG format, a still photo from which the image was
3560scanned, or possibly the subject matter itself. In order to facilitate
3561machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3562tEXt chunk use RFC 1123 format dates (e.g. "22 May 1997 18:07:10 GMT"),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3563although this isn't a requirement. Unlike the tIME chunk, the
3564"Creation Time" tEXt chunk is not expected to be automatically changed
3565by the software. To facilitate the use of RFC 1123 dates, a function
3566png_convert_to_rfc1123(png_timep) is provided to convert from PNG
3567time to an RFC 1123 format string.
3568
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3569.SS Writing unknown chunks
3570
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3571You can use the png_set_unknown_chunks function to queue up chunks
3572for writing. You give it a chunk name, raw data, and a size; that's
3573all there is to it. The chunks will be written by the next following
3574png_write_info_before_PLTE, png_write_info, or png_write_end function.
3575Any chunks previously read into the info structure's unknown-chunk
3576list will also be written out in a sequence that satisfies the PNG
3577specification's ordering rules.
3578
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3579.SS The high-level write interface
3580
3581At this point there are two ways to proceed; through the high-level
3582write interface, or through a sequence of low-level write operations.
3583You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3584in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3585transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3586
3587 PNG_TRANSFORM_IDENTITY No transformation
3588 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3589 PNG_TRANSFORM_PACKSWAP Change order of packed
3590 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3591 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3592 PNG_TRANSFORM_SHIFT Normalize pixels to the
3593 sBIT depth
3594 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
3595 to BGRA
3596 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
3597 to AG
3598 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
3599 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3600 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson1eb14e92008-12-10 07:14:45 -0600[diff] [blame]3601 PNG_TRANSFORM_STRIP_FILLER Strip out filler
3602 bytes (deprecated).
3603 PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
3604 filler bytes
3605 PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing
3606 filler bytes
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3607
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3608If you have valid image data in the info structure (you can use
3609png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3610
3611 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
3612
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3613where png_transforms is an integer containing the bitwise OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3614transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3615followed the set of transformations indicated by the transform mask,
3616then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3617
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3618(The final parameter of this call is not yet used. Someday it might point
3619to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3620
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]3621You must use png_transforms and not call any png_set_transform() functions
3622when you use png_write_png().
3623
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3624.SS The low-level write interface
3625
3626If you are going the low-level route instead, you are now ready to
3627write all the file information up to the actual image data. You do
3628this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3629
3630 png_write_info(png_ptr, info_ptr);
3631
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3632Note that there is one transformation you may need to do before
3633png_write_info(). In PNG files, the alpha channel in an image is the
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3634level of opacity. If your data is supplied as a level of transparency,
3635you can invert the alpha channel before you write it, so that 0 is
3636fully transparent and 255 (in 8-bit or paletted images) or 65535
3637(in 16-bit images) is fully opaque, with
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3638
3639 png_set_invert_alpha(png_ptr);
3640
3641This must appear before png_write_info() instead of later with the
3642other transformations because in the case of paletted images the tRNS
3643chunk data has to be inverted before the tRNS chunk is written. If
3644your image is not a paletted image, the tRNS data (which in such cases
3645represents a single color to be rendered as transparent) won't need to
3646be changed, and you can safely do this transformation after your
3647png_write_info() call.
3648
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3649If you need to write a private chunk that you want to appear before
3650the PLTE chunk when PLTE is present, you can write the PNG info in
3651two steps, and insert code to write your own chunk between them:
3652
3653 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3654 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]3655 png_write_info(png_ptr, info_ptr);
3656
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3657After you've written the file information, you can set up the library
3658to handle any special transformations of the image data. The various
3659ways to transform the data will be described in the order that they
3660should occur. This is important, as some of these change the color
3661type and/or bit depth of the data, and some others only work on
3662certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3663checks to see if it has data that it can do something with, you should
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3664make sure to only enable a transformation if it will be valid for the
3665data. For example, don't swap red and blue on grayscale data.
3666
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3667PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3668the library to strip input data that has 4 or 8 bytes per pixel down
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3669to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
3670bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3671
3672 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
3673
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3674where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3675PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
3676is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3677
3678PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
3679they can, resulting in, for example, 8 pixels per byte for 1 bit files.
3680If the data is supplied at 1 pixel per byte, use this code, which will
3681correctly pack the pixels into a single byte:
3682
3683 png_set_packing(png_ptr);
3684
3685PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
3686data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3687file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3688
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3689 /* Set the true bit depth of the image data */
3690 if (color_type & PNG_COLOR_MASK_COLOR)
3691 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3692 sig_bit.red = true_bit_depth;
3693 sig_bit.green = true_bit_depth;
3694 sig_bit.blue = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3695 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3696
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3697 else
3698 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3699 sig_bit.gray = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3700 }
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3701
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3702 if (color_type & PNG_COLOR_MASK_ALPHA)
3703 {
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3704 sig_bit.alpha = true_bit_depth;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3705 }
3706
3707 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
3708
3709If the data is stored in the row buffer in a bit depth other than
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3710one supported by PNG (e.g. 3 bit data in the range 0-7 for a 4-bit PNG),
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3711this will scale the values to appear to be the correct bit depth as
3712is required by PNG.
3713
3714 png_set_shift(png_ptr, &sig_bit);
3715
3716PNG files store 16 bit pixels in network byte order (big-endian,
3717ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3718supplied the other way (little-endian, i.e. least significant bits
3719first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3720
3721 if (bit_depth > 8)
3722 png_set_swap(png_ptr);
3723
3724If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
3725need to change the order the pixels are packed into bytes, you can use:
3726
3727 if (bit_depth < 8)
3728 png_set_packswap(png_ptr);
3729
3730PNG files store 3 color pixels in red, green, blue order. This code
3731would be used if they are supplied as blue, green, red:
3732
3733 png_set_bgr(png_ptr);
3734
3735PNG files describe monochrome as black being zero and white being
3736one. This code would be used if the pixels are supplied with this reversed
3737(black being one and white being zero):
3738
3739 png_set_invert_mono(png_ptr);
3740
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3741Finally, you can write your own transformation function if none of
3742the existing ones meets your needs. This is done by setting a callback
3743with
3744
3745 png_set_write_user_transform_fn(png_ptr,
3746 write_transform_fn);
3747
3748You must supply the function
3749
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]3750 void write_transform_fn(png_structp png_ptr, png_row_infop
3751 row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3752
3753See pngtest.c for a working example. Your function will be called
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3754before any of the other transformations are processed. If supported
3755libpng also supplies an information routine that may be called from
3756your callback:
3757
3758 png_get_current_row_number(png_ptr);
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame^]3759 png_get_current_pass_number(png_ptr);
John Bowlerf19abd62011-01-22 18:29:24 -0600[diff] [blame]3760
John Bowlercd113452011-02-16 06:15:13 -0600[diff] [blame^]3761This returns the current row passed to the transform. With interlaced
3762images the value returned is the row in the input sub-image image. Use
3763PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
3764find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass).
3765
3766The discussion of interlace handling above contains more information on how to
3767use these values.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3768
3769You can also set up a pointer to a user structure for use by your
3770callback function.
3771
3772 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
3773
3774The user_channels and user_depth parameters of this function are ignored
3775when writing; you can set them to zero as shown.
3776
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3777You can retrieve the pointer via the function png_get_user_transform_ptr().
3778For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3779
3780 voidp write_user_transform_ptr =
3781 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3782
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3783It is possible to have libpng flush any pending output, either manually,
3784or automatically after a certain number of lines have been written. To
3785flush the output stream a single time call:
3786
3787 png_write_flush(png_ptr);
3788
3789and to have libpng flush the output stream periodically after a certain
3790number of scanlines have been written, call:
3791
3792 png_set_flush(png_ptr, nrows);
3793
3794Note that the distance between rows is from the last time png_write_flush()
3795was called, or the first row of the image if it has never been called.
3796So if you write 50 lines, and then png_set_flush 25, it will flush the
3797output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3798png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3799If nrows is too small (less than about 10 lines for a 640 pixel wide
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3800RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3801may be acceptable for real-time applications). Infrequent flushing will
3802only degrade the compression performance by a few percent over images
3803that do not use flushing.
3804
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3805.SS Writing the image data
3806
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3807That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3808The simplest way to do this is in one function call. If you have the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3809whole image in memory, you can just call png_write_image() and libpng
3810will write the image. You will need to pass in an array of pointers to
3811each row. This function automatically handles interlacing, so you don't
3812need to call png_set_interlace_handling() or call this function multiple
3813times, or any of that other stuff necessary with png_write_rows().
3814
3815 png_write_image(png_ptr, row_pointers);
3816
3817where row_pointers is:
3818
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3819 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3820
3821You can point to void or char or whatever you use for pixels.
3822
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3823If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3824use png_write_rows() instead. If the file is not interlaced,
3825this is simple:
3826
3827 png_write_rows(png_ptr, row_pointers,
3828 number_of_rows);
3829
3830row_pointers is the same as in the png_write_image() call.
3831
3832If you are just writing one row at a time, you can do this with
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3833a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3834
3835 png_bytep row_pointer = row;
3836
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3837 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3838
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3839When the file is interlaced, things can get a good deal more complicated.
3840The only currently (as of the PNG Specification version 1.2, dated July
38411999) defined interlacing scheme for PNG files is the "Adam7" interlace
3842scheme, that breaks down an image into seven smaller images of varying
3843size. libpng will build these images for you, or you can do them
3844yourself. If you want to build them yourself, see the PNG specification
3845for details of which pixels to write when.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3846
3847If you don't want libpng to handle the interlacing details, just
3848use png_set_interlace_handling() and call png_write_rows() the
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3849correct number of times to write all the sub-images
3850(png_set_interlace_handling() returns the number of sub-images.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3851
3852If you want libpng to build the sub-images, call this before you start
3853writing any rows:
3854
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3855 number_of_passes = png_set_interlace_handling(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3856
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3857This will return the number of passes needed. Currently, this is seven,
3858but may change if another interlace type is added.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3859
3860Then write the complete image number_of_passes times.
3861
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3862 png_write_rows(png_ptr, row_pointers, number_of_rows);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3863
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]3864Think carefully before you write an interlaced image. Typically code that
3865reads such images reads all the image data into memory, uncompressed, before
3866doing any processing. Only code that can display an image on the fly can
3867take advantage of the interlacing and even then the image has to be exactly
3868the correct size for the output device, because scaling an image requires
3869adjacent pixels and these are not available until all the passes have been
3870read.
3871
3872If you do write an interlaced image you will hardly ever need to handle
3873the interlacing yourself. Call png_set_interlace_handling() and use the
3874approach described above.
3875
3876The only time it is conceivable that you will really need to write an
3877interlaced image pass-by-pass is when you have read one pass by pass and
3878made some pixel-by-pixel transformation to it, as described in the read
3879code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros
3880to determine the size of each sub-image in turn and simply write the rows
3881you obtained from the read code.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3882
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3883.SS Finishing a sequential write
3884
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3885After you are finished writing the image, you should finish writing
3886the file. If you are interested in writing comments or time, you should
3887pass an appropriately filled png_info pointer. If you are not interested,
3888you can pass NULL.
3889
3890 png_write_end(png_ptr, info_ptr);
3891
3892When you are done, you can free all memory used by libpng like this:
3893
3894 png_destroy_write_struct(&png_ptr, &info_ptr);
3895
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3896It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3897point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3898
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3899 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3900
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3901 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3902 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3903 more of
3904 PNG_FREE_PLTE, PNG_FREE_TRNS,
3905 PNG_FREE_HIST, PNG_FREE_ICCP,
3906 PNG_FREE_PCAL, PNG_FREE_ROWS,
3907 PNG_FREE_SCAL, PNG_FREE_SPLT,
3908 PNG_FREE_TEXT, PNG_FREE_UNKN,
3909 or simply PNG_FREE_ALL
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3910
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3911 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3912 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3913
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3914This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3915already been freed, or has not yet been allocated, or was allocated
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3916by the user and not by libpng, and will in those cases do nothing.
3917The "seq" parameter is ignored if only one item of the selected data
3918type, such as PLTE, is allowed. If "seq" is not -1, and multiple items
3919are allowed for the data type identified in the mask, such as text or
3920sPLT, only the n'th item in the structure is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3921
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3922If you allocated data such as a palette that you passed in to libpng
3923with png_set_*, you must not free it until just before the call to
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3924png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3925
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3926The default behavior is only to free data that was allocated internally
3927by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3928or so that it will free data that was allocated by the user with png_malloc()
3929or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3930
3931 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3932
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3933 freer - one of
3934 PNG_DESTROY_WILL_FREE_DATA
3935 PNG_SET_WILL_FREE_DATA
3936 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3937
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3938 mask - which data elements are affected
3939 same choices as in png_free_data()
3940
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3941For example, to transfer responsibility for some data from a read structure
3942to a write structure, you could use
3943
3944 png_data_freer(read_ptr, read_info_ptr,
3945 PNG_USER_WILL_FREE_DATA,
3946 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]3947
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3948 png_data_freer(write_ptr, write_info_ptr,
3949 PNG_DESTROY_WILL_FREE_DATA,
3950 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3951
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3952thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3953immediately afterwards reassigning it once more to the write_destroy
3954function. Having done this, it would then be safe to destroy the read
3955structure and continue to use the PLTE, tRNS, and hIST data in the write
3956structure.
3957
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3958This function only affects data that has already been allocated.
3959You can call this function before calling after the png_set_*() functions
3960to control whether the user or png_destroy_*() is supposed to free the data.
3961When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3962application must use
3963png_free() to free it, and when the user transfers responsibility to libpng
3964for data that the user has allocated, the user must have used png_malloc()
3965or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3966
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3967If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
3968separately, do not transfer responsibility for freeing text_ptr to libpng,
3969because when libpng fills a png_text structure it combines these members with
3970the key member, and png_free_data() will free only text_ptr.key. Similarly,
3971if you transfer responsibility for free'ing text_ptr from libpng to your
3972application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3973For a more compact example of writing a PNG image, see the file example.c.
3974
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3975.SH V. Modifying/Customizing libpng:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3976
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3977There are two issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3978standard things like memory allocation, input/output, and error handling.
3979The second deals with more complicated things like adding new chunks,
3980adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3981Both of those are compile-time issues; that is, they are generally
3982determined at the time the code is written, and there is rarely a need
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3983to provide the user with a means of changing them.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3984
3985Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3986
3987All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3988goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3989in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3990these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3991
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3992Memory allocation is done through the functions png_malloc(), png_calloc(),
3993and png_free(). These currently just call the standard C functions.
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]3994png_calloc() calls png_malloc() and then clears the newly
3995allocated memory to zero. There is limited support for certain systems
3996with segmented memory architectures and the types of pointers declared by
3997png.h match this; you will have to use appropriate pointers in your
3998application. Since it is
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]3999unlikely that the method of handling memory allocation on a platform
4000will change between applications, these functions must be modified in
4001the library at compile time. If you prefer to use a different method
4002of allocating and freeing data, you can use png_create_read_struct_2() or
4003png_create_write_struct_2() to register your own functions as described
4004above. These functions also provide a void pointer that can be retrieved
4005via
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4006
4007 mem_ptr=png_get_mem_ptr(png_ptr);
4008
4009Your replacement memory functions must have prototypes as follows:
4010
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4011 png_voidp malloc_fn(png_structp png_ptr,
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4012 png_alloc_size_t size);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4013
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4014 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4015
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4016Your malloc_fn() must return NULL in case of failure. The png_malloc()
4017function will normally call png_error() if it receives a NULL from the
4018system memory allocator or from your replacement malloc_fn().
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]4019
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4020Your free_fn() will never be called with a NULL ptr, since libpng's
4021png_free() checks for NULL before calling free_fn().
4022
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4023Input/Output in libpng is done through png_read() and png_write(),
4024which currently just call fread() and fwrite(). The FILE * is stored in
4025png_struct and is initialized via png_init_io(). If you wish to change
4026the method of I/O, the library supplies callbacks that you can set
4027through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4028time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4029also provide a void pointer that can be retrieved via the function
4030png_get_io_ptr(). For example:
4031
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4032 png_set_read_fn(png_structp read_ptr,
4033 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4034
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4035 png_set_write_fn(png_structp write_ptr,
4036 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4037 png_flush_ptr output_flush_fn);
4038
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]4039 voidp read_io_ptr = png_get_io_ptr(read_ptr);
4040 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4041
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4042The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4043
4044 void user_read_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]4045 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4046
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4047 void user_write_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]4048 png_bytep data, png_size_t length);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4049
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4050 void user_flush_data(png_structp png_ptr);
4051
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4052The user_read_data() function is responsible for detecting and
4053handling end-of-data errors.
4054
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4055Supplying NULL for the read, write, or flush functions sets them back
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4056to using the default C stream functions, which expect the io_ptr to
4057point to a standard *FILE structure. It is probably a mistake
4058to use NULL for one of write_data_fn and output_flush_fn but not both
4059of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
4060It is an error to read from a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4061
4062Error handling in libpng is done through png_error() and png_warning().
4063Errors handled through png_error() are fatal, meaning that png_error()
4064should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4065setjmp() and longjmp() (unless you have compiled libpng with
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4066PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()),
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]4067but you could change this to do things like exit() if you should wish,
Glenn Randers-Pehrson54ac9a92010-04-02 17:06:22 -0500[diff] [blame]4068as long as your function does not return.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4069
4070On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4071to print a warning message, and then control returns to the calling code.
4072By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]4073fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
4074(because you don't want the messages) or PNG_NO_STDIO defined (because
4075fprintf() isn't available). If you wish to change the behavior of the error
4076functions, you will need to set up your own message callbacks. These
4077functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4078It is also possible to redirect errors and warnings to your own replacement
4079functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4080
4081 png_set_error_fn(png_structp png_ptr,
4082 png_voidp error_ptr, png_error_ptr error_fn,
4083 png_error_ptr warning_fn);
4084
4085 png_voidp error_ptr = png_get_error_ptr(png_ptr);
4086
4087If NULL is supplied for either error_fn or warning_fn, then the libpng
4088default function will be used, calling fprintf() and/or longjmp() if a
4089problem is encountered. The replacement error functions should have
4090parameters as follows:
4091
4092 void user_error_fn(png_structp png_ptr,
4093 png_const_charp error_msg);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4094
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4095 void user_warning_fn(png_structp png_ptr,
4096 png_const_charp warning_msg);
4097
4098The motivation behind using setjmp() and longjmp() is the C++ throw and
4099catch exception handling methods. This makes the code much easier to write,
4100as there is no need to check every return code of every function call.
4101However, there are some uncertainties about the status of local variables
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4102after a longjmp, so the user may want to be careful about doing anything
4103after setjmp returns non-zero besides returning itself. Consult your
4104compiler documentation for more details. For an alternative approach, you
4105may wish to use the "cexcept" facility (see http://cexcept.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4106
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4107.SS Custom chunks
4108
4109If you need to read or write custom chunks, you may need to get deeper
4110into the libpng code. The library now has mechanisms for storing
4111and writing chunks of unknown type; you can even declare callbacks
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]4112for custom chunks. However, this may not be good enough if the
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4113library code itself needs to know about interactions between your
4114chunk and existing `intrinsic' chunks.
4115
4116If you need to write a new intrinsic chunk, first read the PNG
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4117specification. Acquire a first level of understanding of how it works.
4118Pay particular attention to the sections that describe chunk names,
4119and look at how other chunks were designed, so you can do things
4120similarly. Second, check out the sections of libpng that read and
4121write chunks. Try to find a chunk that is similar to yours and use
4122it as a template. More details can be found in the comments inside
4123the code. It is best to handle unknown chunks in a generic method,
4124via callback functions, instead of by modifying libpng functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4125
4126If you wish to write your own transformation for the data, look through
4127the part of the code that does the transformations, and check out some of
4128the simpler ones to get an idea of how they work. Try to find a similar
4129transformation to the one you want to add and copy off of it. More details
4130can be found in the comments inside the code itself.
4131
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4132.SS Configuring for 16 bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4133
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4134You will want to look into zconf.h to tell zlib (and thus libpng) that
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4135it cannot allocate more then 64K at a time. Even if you can, the memory
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4136won't be accessible. So limit zlib and libpng to 64K by defining MAXSEG_64K.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4137
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4138.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4139
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4140For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4141have to limit zlib's memory usage via a png_set_compression_mem_level()
4142call. See zlib.h or zconf.h in the zlib library for more information.
4143
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4144.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4145
4146Libpng's support for medium model has been tested on most of the popular
4147compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
4148defined, and FAR gets defined to far in pngconf.h, and you should be
4149all set. Everything in the library (except for zlib's structure) is
4150expecting far data. You must use the typedefs with the p or pp on
4151the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4152note that the rows of data are defined as png_bytepp, which is an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4153unsigned char far * far *.
4154
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4155.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4156
4157You will need to write new error and warning functions that use the GUI
4158interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]4159warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4160in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4161They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4162you may also have to change the memory allocators (png_malloc, etc.).
4163
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4164.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4165
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]4166All includes for libpng are in pngconf.h. If you need to add, change
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4167or delete an include, this is the place to do it.
4168The includes that are not needed outside libpng are placed in pngpriv.h,
4169which is only used by the routines inside libpng itself.
4170The files in libpng proper only include pngpriv.h and png.h, which
4171in turn includes pngconf.h.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4172
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4173.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4174
4175There are special functions to configure the compression. Perhaps the
4176most useful one changes the compression level, which currently uses
4177input compression values in the range 0 - 9. The library normally
4178uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
4179have shown that for a large majority of images, compression values in
4180the range 3-6 compress nearly as well as higher levels, and do so much
4181faster. For online applications it may be desirable to have maximum speed
4182(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
4183specify no compression (Z_NO_COMPRESSION = 0), but this would create
4184files larger than just storing the raw bitmap. You can specify the
4185compression level by calling:
4186
4187 png_set_compression_level(png_ptr, level);
4188
4189Another useful one is to reduce the memory level used by the library.
4190The memory level defaults to 8, but it can be lowered if you are
4191short on memory (running DOS, for example, where you only have 640K).
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4192Note that the memory level does have an effect on compression; among
4193other things, lower levels will result in sections of incompressible
4194data being emitted in smaller stored blocks, with a correspondingly
4195larger relative overhead of up to 15% in the worst case.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4196
4197 png_set_compression_mem_level(png_ptr, level);
4198
4199The other functions are for configuring zlib. They are not recommended
4200for normal use and may result in writing an invalid PNG file. See
4201zlib.h for more information on what these mean.
4202
4203 png_set_compression_strategy(png_ptr,
4204 strategy);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4205
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4206 png_set_compression_window_bits(png_ptr,
4207 window_bits);
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4208
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4209 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4210 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4211
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4212.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4213
4214If you want to control whether libpng uses filtering or not, which
4215filters are used, and how it goes about picking row filters, you
4216can call one of these functions. The selection and configuration
4217of row filters can have a significant impact on the size and
4218encoding speed and a somewhat lesser impact on the decoding speed
4219of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4220images (with and without alpha), but not for paletted images nor
4221for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4222
4223The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4224currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4225parameter sets which filter(s), if any, should be used for each
4226scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
4227to turn filtering on and off, respectively.
4228
4229Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
4230PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]4231ORed together with '|' to specify one or more filters to use.
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4232These filters are described in more detail in the PNG specification.
4233If you intend to change the filter type during the course of writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4234the image, you should start with flags set for all of the filters
4235you intend to use so that libpng can initialize its internal
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4236structures appropriately for all of the filter types. (Note that this
4237means the first row must always be adaptively filtered, because libpng
4238currently does not allocate the filter buffers until png_write_row()
4239is called for the first time.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4240
4241 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4242 PNG_FILTER_UP | PNG_FILTER_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4243 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4244
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4245 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
4246 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4247 The second parameter can also be
4248 PNG_INTRAPIXEL_DIFFERENCING if you are
4249 writing a PNG to be embedded in a MNG
4250 datastream. This parameter must be the
4251 same as the value of filter_method used
4252 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4253
4254It is also possible to influence how libpng chooses from among the
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4255available filters. This is done in one or both of two ways - by
4256telling it how important it is to keep the same filter for successive
4257rows, and by telling it the relative computational costs of the filters.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4258
4259 double weights[3] = {1.5, 1.3, 1.1},
4260 costs[PNG_FILTER_VALUE_LAST] =
4261 {1.0, 1.3, 1.3, 1.5, 1.7};
4262
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4263 png_set_filter_heuristics(png_ptr,
4264 PNG_FILTER_HEURISTIC_WEIGHTED, 3,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4265 weights, costs);
4266
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4267The weights are multiplying factors that indicate to libpng that the
4268row filter should be the same for successive rows unless another row filter
4269is that many times better than the previous filter. In the above example,
4270if the previous 3 filters were SUB, SUB, NONE, the SUB filter could have a
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4271"sum of absolute differences" 1.5 x 1.3 times higher than other filters
4272and still be chosen, while the NONE filter could have a sum 1.1 times
4273higher than other filters and still be chosen. Unspecified weights are
4274taken to be 1.0, and the specified weights should probably be declining
4275like those above in order to emphasize recent filters over older filters.
4276
4277The filter costs specify for each filter type a relative decoding cost
4278to be considered when selecting row filters. This means that filters
4279with higher costs are less likely to be chosen over filters with lower
4280costs, unless their "sum of absolute differences" is that much smaller.
4281The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4282the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4283size.
4284
4285Note that the numbers above were invented purely for this example and
4286are given only to help explain the function usage. Little testing has
4287been done to find optimum values for either the costs or the weights.
4288
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4289.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4290
4291There are a bunch of #define's in pngconf.h that control what parts of
4292libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4293never going to use a capability, you can change the #define to #undef
4294before recompiling libpng and save yourself code and data space, or
4295you can turn off individual capabilities with defines that begin with
4296PNG_NO_.
4297
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4298In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead.
4299
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4300You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]4301off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]4302PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
4303or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4304along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4305want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable the extra
4306transformations but still leave the library fully capable of reading
4307and writing PNG files with all known public chunks. Use of the
4308PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive produces a library
4309that is incapable of reading or writing ancillary chunks. If you are
4310not using the progressive reading capability, you can turn that off
4311with PNG_NO_PROGRESSIVE_READ (don't confuse this with the INTERLACING
4312capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4313
4314All the reading and writing specific code are in separate files, so the
4315linker should only grab the files it needs. However, if you want to
4316make sure, or if you are building a stand alone library, all the
4317reading files start with pngr and all the writing files start with
4318pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
4319are used for both reading and writing, and always need to be included.
4320The progressive reader is in pngpread.c
4321
4322If you are creating or distributing a dynamically linked library (a .so
4323or DLL file), you should not remove or disable any parts of the library,
4324as this will cause applications linked with different versions of the
4325library to fail if they call functions not available in your library.
4326The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4327those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4328
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]4329.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4330
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4331The macro definition PNG_DEBUG can be used to request debugging
4332printout. Set it to an integer value in the range 0 to 3. Higher
4333numbers result in increasing amounts of debugging information. The
4334information is printed to the "stderr" file, unless another file
4335name is specified in the PNG_DEBUG_FILE macro definition.
4336
4337When PNG_DEBUG > 0, the following functions (macros) become available:
4338
4339 png_debug(level, message)
4340 png_debug1(level, message, p1)
4341 png_debug2(level, message, p1, p2)
4342
4343in which "level" is compared to PNG_DEBUG to decide whether to print
4344the message, "message" is the formatted string to be printed,
4345and p1 and p2 are parameters that are to be embedded in the string
4346according to printf-style formatting directives. For example,
4347
4348 png_debug1(2, "foo=%d\n", foo);
4349
4350is expanded to
4351
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4352 if (PNG_DEBUG > 2)
4353 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4354
4355When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
4356can still use PNG_DEBUG to control your own debugging:
4357
4358 #ifdef PNG_DEBUG
4359 fprintf(stderr, ...
4360 #endif
4361
4362When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
4363having level = 0 will be printed. There aren't any such statements in
4364this version of libpng, but if you insert some they will be printed.
4365
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]4366.SH VI. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4367
4368The MNG specification (available at http://www.libpng.org/pub/mng) allows
4369certain extensions to PNG for PNG images that are embedded in MNG datastreams.
4370Libpng can support some of these extensions. To enable them, use the
4371png_permit_mng_features() function:
4372
4373 feature_set = png_permit_mng_features(png_ptr, mask)
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4374
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4375 mask is a png_uint_32 containing the bitwise OR of the
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4376 features you want to enable. These include
4377 PNG_FLAG_MNG_EMPTY_PLTE
4378 PNG_FLAG_MNG_FILTER_64
4379 PNG_ALL_MNG_FEATURES
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4380
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]4381 feature_set is a png_uint_32 that is the bitwise AND of
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]4382 your mask with the set of MNG features that is
4383 supported by the version of libpng that you are using.
4384
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4385It is an error to use this function when reading or writing a standalone
4386PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]4387in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
4388and the MHDR and MEND chunks. Libpng does not provide support for these
4389or any other MNG chunks; your application must provide its own support for
4390them. You may wish to consider using libmng (available at
4391http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]4392
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]4393.SH VII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4394
4395It should be noted that versions of libpng later than 0.96 are not
4396distributed by the original libpng author, Guy Schalnat, nor by
4397Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
4398distributed versions 0.89 through 0.96, but rather by another member
4399of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
4400still alive and well, but they have moved on to other things.
4401
4402The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]4403png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4404moved to PNG_INTERNAL in version 0.95 to discourage their use. These
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4405functions will be removed from libpng version 1.4.0.
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4406
4407The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4408via the png_create_read_struct(), png_create_write_struct(), and
4409png_create_info_struct() because they isolate the size of the structures
4410from the application, allow version error checking, and also allow the
4411use of custom error handling routines during the initialization, which
4412the old functions do not. The functions png_read_destroy() and
4413png_write_destroy() do not actually free the memory that libpng
4414allocated for these structs, but just reset the data structures, so they
4415can be used instead of png_destroy_read_struct() and
4416png_destroy_write_struct() if you feel there is too much system overhead
4417allocating and freeing the png_struct for each image read.
4418
4419Setting the error callbacks via png_set_message_fn() before
4420png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]4421because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4422to fail if the png_ptr was not initialized to zero. It is still possible
4423to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]4424png_set_error_fn(), which is essentially the same function, but with a new
4425name to force compilation errors with applications that try to use the old
4426method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4427
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]4428Starting with version 1.0.7, you can find out which version of the library
4429you are using at run-time:
4430
4431 png_uint_32 libpng_vn = png_access_version_number();
4432
4433The number libpng_vn is constructed from the major version, minor
4434version with leading zero, and release number with leading zero,
4435(e.g., libpng_vn for version 1.0.7 is 10007).
4436
4437You can also check which version of png.h you used when compiling your
4438application:
4439
4440 png_uint_32 application_vn = PNG_LIBPNG_VER;
4441
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4442.SH VIII. Changes to Libpng from version 1.0.x to 1.2.x
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4443
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4444Support for user memory management was enabled by default. To
4445accomplish this, the functions png_create_read_struct_2(),
4446png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
4447png_malloc_default(), and png_free_default() were added.
4448
Glenn Randers-Pehrsond6ea40a2009-11-02 07:32:00 -0600[diff] [blame]4449Support for the iTXt chunk has been enabled by default as of
4450version 1.2.41.
4451
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4452Support for certain MNG features was enabled.
4453
4454Support for numbered error messages was added. However, we never got
4455around to actually numbering the error messages. The function
4456png_set_strip_error_numbers() was added (Note: the prototype for this
4457function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
4458builds of libpng-1.2.15. It was restored in libpng-1.2.36).
4459
4460The png_malloc_warn() function was added at libpng-1.2.3. This issues
4461a png_warning and returns NULL instead of aborting when it fails to
4462acquire the requested memory allocation.
4463
4464Support for setting user limits on image width and height was enabled
4465by default. The functions png_set_user_limits(), png_get_user_width_max(),
4466and png_get_user_height_max() were added at libpng-1.2.6.
4467
4468The png_set_add_alpha() function was added at libpng-1.2.7.
4469
4470The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
4471Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
4472tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
4473deprecated.
4474
4475A number of macro definitions in support of runtime selection of
4476assembler code features (especially Intel MMX code support) were
4477added at libpng-1.2.0:
4478
4479 PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
4480 PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
4481 PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
4482 PNG_ASM_FLAG_MMX_READ_INTERLACE
4483 PNG_ASM_FLAG_MMX_READ_FILTER_SUB
4484 PNG_ASM_FLAG_MMX_READ_FILTER_UP
4485 PNG_ASM_FLAG_MMX_READ_FILTER_AVG
4486 PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
4487 PNG_ASM_FLAGS_INITIALIZED
4488 PNG_MMX_READ_FLAGS
4489 PNG_MMX_FLAGS
4490 PNG_MMX_WRITE_FLAGS
4491 PNG_MMX_FLAGS
4492
4493We added the following functions in support of runtime
4494selection of assembler code features:
4495
4496 png_get_mmx_flagmask()
4497 png_set_mmx_thresholds()
4498 png_get_asm_flags()
4499 png_get_mmx_bitdepth_threshold()
4500 png_get_mmx_rowbytes_threshold()
4501 png_set_asm_flags()
4502
4503We replaced all of these functions with simple stubs in libpng-1.2.20,
4504when the Intel assembler code was removed due to a licensing issue.
4505
Glenn Randers-Pehrson3d893a02009-08-31 13:32:46 -0500[diff] [blame]4506These macros are deprecated:
4507
4508 PNG_READ_TRANSFORMS_NOT_SUPPORTED
4509 PNG_PROGRESSIVE_READ_NOT_SUPPORTED
4510 PNG_NO_SEQUENTIAL_READ_SUPPORTED
4511 PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
4512 PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
4513 PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
4514
4515They have been replaced, respectively, by:
4516
4517 PNG_NO_READ_TRANSFORMS
4518 PNG_NO_PROGRESSIVE_READ
4519 PNG_NO_SEQUENTIAL_READ
4520 PNG_NO_WRITE_TRANSFORMS
4521 PNG_NO_READ_ANCILLARY_CHUNKS
4522 PNG_NO_WRITE_ANCILLARY_CHUNKS
4523
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4524PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been
4525deprecated since libpng-1.0.16 and libpng-1.2.6.
4526
4527The function
4528 png_check_sig(sig, num)
4529was replaced with
4530 !png_sig_cmp(sig, 0, num)
4531It has been deprecated since libpng-0.90.
4532
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4533The function
4534 png_set_gray_1_2_4_to_8()
4535which also expands tRNS to alpha was replaced with
4536 png_set_expand_gray_1_2_4_to_8()
4537which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4538
Glenn Randers-Pehrsond740c842009-11-04 19:01:54 -0600[diff] [blame]4539.SH IX. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
4540
4541Private libpng prototypes and macro definitions were moved from
4542png.h and pngconf.h into a new pngpriv.h header file.
4543
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4544Functions png_set_benign_errors(), png_benign_error(), and
4545png_chunk_benign_error() were added.
4546
4547Support for setting the maximum amount of memory that the application
4548will allocate for reading chunks was added, as a security measure.
4549The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
4550were added to the library.
4551
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]4552We implemented support for I/O states by adding png_ptr member io_state
4553and functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4554
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4555We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
4556input transforms.
4557
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4558Checking for and reporting of errors in the IHDR chunk is more thorough.
4559
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4560Support for global arrays was removed, to improve thread safety.
4561
4562Some obsolete/deprecated macros and functions have been removed.
4563
4564Typecasted NULL definitions such as
4565 #define png_voidp_NULL (png_voidp)NULL
4566were eliminated. If you used these in your application, just use
4567NULL instead.
4568
4569The png_struct and info_struct members "trans" and "trans_values" were
4570changed to "trans_alpha" and "trans_color", respectively.
4571
4572The obsolete, unused pnggccrd.c and pngvcrd.c files and related makefiles
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4573were removed.
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4574
4575The PNG_1_0_X and PNG_1_2_X macros were eliminated.
4576
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]4577The PNG_LEGACY_SUPPORTED macro was eliminated.
4578
4579Many WIN32_WCE #ifdefs were removed.
4580
4581The functions png_read_init(info_ptr), png_write_init(info_ptr),
4582png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
4583have been removed. They have been deprecated since libpng-0.95.
4584
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4585The png_permit_empty_plte() was removed. It has been deprecated
4586since libpng-1.0.9. Use png_permit_mng_features() instead.
4587
4588We removed the obsolete stub functions png_get_mmx_flagmask(),
4589png_set_mmx_thresholds(), png_get_asm_flags(),
4590png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
4591png_set_asm_flags(), and png_mmx_supported()
4592
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4593We removed the obsolete png_check_sig(), png_memcpy_check(), and
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]4594png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(),
4595and memset(), respectively.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4596
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4597The function png_set_gray_1_2_4_to_8() was removed. It has been
4598deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with
4599png_set_expand_gray_1_2_4_to_8() because the former function also
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]4600expanded any tRNS chunk to an alpha channel.
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4601
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4602Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32
4603were added and are used by default instead of the corresponding
4604functions. Unfortunately,
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]4605from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4606function) incorrectly returned a value of type png_uint_32.
4607
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4608We changed the prototype for png_malloc() from
4609 png_malloc(png_structp png_ptr, png_uint_32 size)
4610to
4611 png_malloc(png_structp png_ptr, png_alloc_size_t size)
4612
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]4613This also applies to the prototype for the user replacement malloc_fn().
4614
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4615The png_calloc() function was added and is used in place of
Glenn Randers-Pehrson2be8b642010-07-29 19:09:18 -0500[diff] [blame]4616of "png_malloc(); memset();" except in the case in png_read_png()
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4617where the array consists of pointers; in this case a "for" loop is used
4618after the png_malloc() to set the pointers to NULL, to give robust.
4619behavior in case the application runs out of memory part-way through
4620the process.
4621
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4622We changed the prototypes of png_get_compression_buffer_size() and
4623png_set_compression_buffer_size() to work with png_size_t instead of
4624png_uint_32.
4625
Glenn Randers-Pehrson45af8192009-12-30 08:37:29 -0600[diff] [blame]4626Support for numbered error messages was removed by default, since we
4627never got around to actually numbering the error messages. The function
4628png_set_strip_error_numbers() was removed from the library by default.
4629
4630The png_zalloc() and png_zfree() functions are no longer exported.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4631The png_zalloc() function no longer zeroes out the memory that it
4632allocates.
4633
Glenn Randers-Pehrson3cd7cff2010-04-16 19:27:08 -0500[diff] [blame]4634Support for dithering was disabled by default in libpng-1.4.0, because
4635been well tested and doesn't actually "dither". The code was not
4636removed, however, and could be enabled by building libpng with
4637PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support
4638was reenabled, but the function was renamed png_set_quantize() to
4639reflect more accurately what it actually does. At the same time,
4640the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4641PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED
4642was renamed to PNG_READ_QUANTIZE_SUPPORTED.
Glenn Randers-Pehrson60988072010-04-13 22:11:06 -0500[diff] [blame]4643
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]4644We removed the trailing '.' from the warning and error messages.
4645
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4646.SH X. Changes to Libpng from version 1.4.x to 1.5.x
4647
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]4648From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4649function) incorrectly returned a value of type png_uint_32.
4650
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4651A. Changes that affect users of libpng
4652
4653There are no substantial API changes between the non-deprecated parts of
4654the 1.4.5 API and the 1.5.0 API, however the ability to directly access
4655the main libpng control structures, png_struct and png_info, deprecated
4656in earlier versions of libpng, has been completely removed from
4657libpng 1.5.
4658
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]4659We no longer include zlib.h in png.h. Applications that need access
4660to information in zlib.h will need to add the '#include "zlib.h"'
4661directive. It does not matter whether it is placed prior to or after
4662the '"#include png.h"' directive.
4663
4664We moved the png_strcpy(), png_strncpy(), png_strlen(), png_memcpy(),
4665png_memcmp(), png_sprintf, and png_memcpy() macros into a private
4666header file (pngpriv.h) that is not accessible to applications.
4667
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]4668In png_get_iCCP, the type of "profile" was changed from png_charpp
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4669to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep.
Glenn Randers-Pehrson9d23b402011-01-08 10:42:01 -0600[diff] [blame]4670
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4671There are changes of form in png.h, including new and changed macros to
4672declare
Glenn Randers-Pehrsonf5ea1b72011-01-06 06:42:51 -0600[diff] [blame]4673parts of the API. Some API functions with arguments that are pointers to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4674data not modified within the function have been corrected to declare
4675these arguments with PNG_CONST.
4676
4677Much of the internal use of C macros to control the library build has also
4678changed and some of this is visible in the exported header files, in
4679particular the use of macros to control data and API elements visible
4680during application compilation may require significant revision to
4681application code. (It is extremely rare for an application to do this.)
4682
4683Any program that compiled against libpng 1.4 and did not use deprecated
4684features or access internal library structures should compile and work
4685against libpng 1.5.
4686
Glenn Randers-Pehrson6e974102010-12-19 16:44:22 -0600[diff] [blame]4687libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of
4688interlaced images. The macros return the number of rows and columns in
4689each pass and information that can be used to de-interlace and (if
4690absolutely necessary) interlace an image.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4691
4692libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls
4693the application provided png_longjmp_ptr on the internal, but application
4694initialized, jmpbuf. It is provided as a convenience to avoid the need
4695to use the png_jmpbuf macro, which had the unnecessary side effect of
4696resetting the internal png_longjmp_ptr value.
4697
4698libpng 1.5.0 includes a complete fixed point API. By default this is
4699present along with the corresponding floating point API. In general the
4700fixed point API is faster and smaller than the floating point one because
4701the PNG file format used fixed point, not floating point. This applies
4702even if the library uses floating point in internal calculations. A new
4703macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library
4704uses floating point arithmetic (the default) or fixed point arithmetic
4705internally for performance critical calculations such as gamma correction.
Glenn Randers-Pehrson00879b12011-01-15 19:25:34 -0600[diff] [blame]4706In some cases, the gamma calculations may produce slightly different
4707results. This has changed the results in png_rgb_to_gray and in alpha
4708composition (png_set_background for example). This applies even if the
4709original image was already linear (gamma == 1.0) and, therefore, it is
4710not necessary to linearize the image. This is because libpng has *not*
4711been changed to optimize that case correctly, yet.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4712
4713Fixed point support for the sCAL chunk comes with an important caveat;
4714the sCAL specification uses a decimal encoding of floating point values
4715and the accuracy of PNG fixed point values is insufficient for
4716representation of these values. Consequently a "string" API
4717(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading
4718arbitrary sCAL chunks in the absence of either the floating point API or
4719internal floating point calculations.
4720
4721Applications no longer need to include the optional distribution header
4722file pngusr.h or define the corresponding macros during application
4723build in order to see the correct variant of the libpng API. From 1.5.0
4724application code can check for the corresponding _SUPPORTED macro:
4725
4726#ifdef PNG_INCH_CONVERSIONS_SUPPORTED
4727 /* code that uses the inch conversion APIs. */
4728#endif
4729
4730This macro will only be defined if the inch conversion functions have been
4731compiled into libpng. The full set of macros, and whether or not support
4732has been compiled in, are available in the header file pnglibconf.h.
4733This header file is specific to the libpng build. Notice that prior to
47341.5.0 the _SUPPORTED macros would always have the default definition unless
4735reset by pngusr.h or by explicit settings on the compiler command line.
4736These settings may produce compiler warnings or errors in 1.5.0 because
4737of macro redefinition.
4738
Glenn Randers-Pehrsonc36bb792011-02-12 09:49:07 -0600[diff] [blame]4739From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4740function) incorrectly returned a value of type png_uint_32. libpng 1.5.0
4741is consistent with the implementation in 1.4.5 and 1.2.x (where the macro
4742did not exist.)
4743
4744Applications can now choose whether to use these macros or to call the
4745corresponding function by defining PNG_USE_READ_MACROS or
4746PNG_NO_USE_READ_MACROS before including png.h. Notice that this is
4747only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0
4748 will lead to a link failure.
Glenn Randers-Pehrson59fa3e92011-01-06 07:07:06 -0600[diff] [blame]4749
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4750B. Changes to the build and configuration of libpng
4751
4752Details of internal changes to the library code can be found in the CHANGES
4753file. These will be of no concern to the vast majority of library users or
4754builders, however the few who configure libpng to a non-default feature
4755set may need to change how this is done.
4756
4757There should be no need for library builders to alter build scripts if
4758these use the distributed build support - configure or the makefiles -
4759however users of the makefiles may care to update their build scripts
4760to build pnglibconf.h where the corresponding makefile does not do so.
4761
4762Building libpng with a non-default configuration has changed completely.
4763The old method using pngusr.h should still work correctly even though the
4764way pngusr.h is used in the build has been changed, however library
4765builders will probably want to examine the changes to take advantage of
4766new capabilities and to simplify their build system.
4767
4768B.1 Specific changes to library configuration capabilities
4769
4770The library now supports a complete fixed point implementation and can
4771thus be used on systems which have no floating point support or very
4772limited or slow support. Previously gamma correction, an essential part
4773of complete PNG support, required reasonably fast floating point.
4774
4775As part of this the choice of internal implementation has been made
4776independent of the choice of fixed versus floating point APIs and all the
4777missing fixed point APIs have been implemented.
4778
4779The exact mechanism used to control attributes of API functions has
4780changed. A single set of operating system independent macro definitions
4781is used and operating system specific directives are defined in
4782pnglibconf.h
4783
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4784As part of this the mechanism used to choose procedure call standards on
4785those systems that allow a choice has been changed. At present this only
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4786affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems
4787running on Intel processors. As before PNGAPI is defined where required
4788to control the exported API functions; however, two new macros, PNGCBAPI
4789and PNGCAPI, are used instead for callback functions (PNGCBAPI) and
4790(PNGCAPI) for functions that must match a C library prototype (currently
4791only png_longjmp_ptr, which must match the C longjmp function.) The new
4792approach is documented in pngconf.h
4793
4794Despite these changes libpng 1.5.0 only supports the native C function
4795calling standard on those platforms tested so far (__cdecl on Microsoft
4796Windows). This is because the support requirements for alternative
4797calling conventions seem to no longer exist. Developers who find it
4798necessary to set PNG_API_RULE to 1 should advise the mailing list
4799(png-mng-implement) of this and library builders who use Openwatcom and
4800therefore set PNG_API_RULE to 2 should also contact the mailing list.
4801
4802A new test program, pngvalid, is provided in addition to pngtest.
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4803pngvalid validates the arithmetic accuracy of the gamma correction
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4804calculations and includes a number of validations of the file format.
4805A subset of the full range of tests is run when "make check" is done
4806(in the 'configure' build.) pngvalid also allows total allocated memory
4807usage to be evaluated and performs additional memory overwrite validation.
4808
4809Many changes to individual feature macros have been made. The following
4810are the changes most likely to be noticed by library builders who
4811configure libpng:
4812
48131) All feature macros now have consistent naming:
4814
4815#define PNG_NO_feature turns the feature off
4816#define PNG_feature_SUPPORTED turns the feature on
4817
4818pnglibconf.h contains one line for each feature macro which is either:
4819
4820#define PNG_feature_SUPPORTED
4821
4822if the feature is supported or:
4823
4824/*#undef PNG_feature_SUPPORTED*/
4825
4826if it is not. Library code consistently checks for the 'SUPPORTED' macro.
4827It does not, and should not, check for the 'NO' macro which will not
4828normally be defined even if the feature is not supported.
4829
4830Compatibility with the old names is provided as follows:
4831
4832PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED
4833
4834And the following definitions disable the corresponding feature:
4835
4836PNG_SETJMP_NOT_SUPPORTED disables SETJMP
4837PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS
4838PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV
4839PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS
4840PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS
4841PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS
4842
4843Library builders should remove use of the above, inconsistent, names.
4844
48452) Warning and error message formatting was previously conditional on
4846the STDIO feature. The library has been changed to use the
4847CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled
4848the library no longer uses the printf(3) functions, even though the
4849default read/write implementations use (FILE) style stdio.h functions.
4850
48513) Three feature macros now control the fixed/floating point decisions:
4852
4853PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs
4854
4855PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in
4856practice these are normally required internally anyway (because the PNG
4857file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT
4858merely stops the function from being exported.
4859
4860PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating
4861point implementation or the fixed point one. Typically the fixed point
4862implementation is larger and slower than the floating point implementation
4863on a system that supports floating point, however it may be faster on a
4864system which lacks floating point hardware and therefore uses a software
4865emulation.
4866
48674) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the
4868functions to read and write ints to be disabled independently of
4869PNG_USE_READ_MACROS, which allows libpng to be built with the functions
4870even though the default is to use the macros - this allows applications
4871to choose at app buildtime whether or not to use macros (previously
4872impossible because the functions weren't in the default build.)
4873
4874B.2 Changes to the configuration mechanism
4875
4876Prior to libpng-1.5.0 library builders who needed to configure libpng
4877had either to modify the exported pngconf.h header file to add system
4878specific configuration or had to write feature selection macros into
4879pngusr.h and cause this to be included into pngconf.h by defining
4880PNG_USER_CONFIG. The latter mechanism had the disadvantage that an
4881application built without PNG_USER_CONFIG defined would see the
4882unmodified, default, libpng API and thus would probably fail to link.
4883
4884These mechanisms still work in the configure build and in any makefile
4885build that builds pnglibconf.h although the feature selection macros
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4886have changed somewhat as described above. In 1.5.0, however, pngusr.h is
4887processed only once, when the exported header file pnglibconf.h is built.
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]4888pngconf.h no longer includes pngusr.h, therefore it is ignored after the
4889build of pnglibconf.h and it is never included in an application build.
4890
4891The rarely used alternative of adding a list of feature macros to the
4892CFLAGS setting in the build also still works, however the macros will be
4893copied to pnglibconf.h and this may produce macro redefinition warnings
4894when the individual C files are compiled.
4895
4896All configuration now only works if pnglibconf.h is built from
4897scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan
4898(the original author of awk) maintains C source code of that awk and this
4899and all known later implementations (often called by subtly different
4900names - nawk and gawk for example) are adequate to build pnglibconf.h.
4901The Sun Microsystems (now Oracle) program 'awk' is an earlier version
4902and does not work, this may also apply to other systems that have a
4903functioning awk called 'nawk'.
4904
4905Configuration options are now documented in scripts/pnglibconf.dfa. This
4906file also includes dependency information that ensures a configuration is
4907consistent; that is, if a feature is switched off dependent features are
4908also removed. As a recommended alternative to using feature macros in
4909pngusr.h a system builder may also define equivalent options in pngusr.dfa
4910(or, indeed, any file) and add that to the configuration by setting
4911DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate
4912how to do this, and a case where pngusr.h is still required.
4913
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4914.SH XI. Detecting libpng
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]4915
4916The png_get_io_ptr() function has been present since libpng-0.88, has never
4917changed, and is unaffected by conditional compilation macros. It is the
4918best choice for use in configure scripts for detecting the presence of any
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]4919libpng version since 0.88. In an autoconf "configure.in" you could use
4920
4921 AC_CHECK_LIB(png, png_get_io_ptr, ...
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]4922
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4923.SH XII. Source code repository
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4924
4925Since about February 2009, version 1.2.34, libpng has been under "git" source
4926control. The git repository was built from old libpng-x.y.z.tar.gz files
4927going back to version 0.70. You can access the git repository (read only)
4928at
4929
4930 git://libpng.git.sourceforge.net/gitroot/libpng
4931
4932or you can browse it via "gitweb" at
4933
4934 http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng
4935
4936Patches can be sent to glennrp at users.sourceforge.net or to
4937png-mng-implement at lists.sourceforge.net or you can upload them to
4938the libpng bug tracker at
4939
4940 http://libpng.sourceforge.net
4941
Glenn Randers-Pehrson7bc25012011-01-21 23:29:09 -0600[diff] [blame]4942We also accept patches built from the tar or zip distributions, and
4943simple verbal discriptions of bug fixes, reported either to the
4944SourceForge bug tracker or to the png-mng-implement at lists.sf.net
4945mailing list.
4946
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]4947.SH XIII. Coding style
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4948
4949Our coding style is similar to the "Allman" style, with curly
4950braces on separate lines:
4951
4952 if (condition)
4953 {
4954 action;
4955 }
4956
4957 else if (another condition)
4958 {
4959 another action;
4960 }
4961
4962The braces can be omitted from simple one-line actions:
4963
4964 if (condition)
4965 return (0);
4966
4967We use 3-space indentation, except for continued statements which
4968are usually indented the same as the first line of the statement
4969plus four more spaces.
4970
Glenn Randers-Pehrson5ade7ed2009-09-30 15:11:49 -0500[diff] [blame]4971For macro definitions we use 2-space indentation, always leaving the "#"
4972in the first column.
4973
4974 #ifndef PNG_NO_FEATURE
4975 # ifndef PNG_FEATURE_SUPPORTED
4976 # define PNG_FEATURE_SUPPORTED
4977 # endif
4978 #endif
4979
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4980Comments appear with the leading "/*" at the same indentation as
4981the statement that follows the comment:
4982
4983 /* Single-line comment */
4984 statement;
4985
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]4986 /* This is a multiple-line
4987 * comment.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4988 */
4989 statement;
4990
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]4991Very short comments can be placed after the end of the statement
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4992to which they pertain:
4993
4994 statement; /* comment */
4995
4996We don't use C++ style ("//") comments. We have, however,
4997used them in the past in some now-abandoned MMX assembler
4998code.
4999
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]5000Functions and their curly braces are not indented, and
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5001exported functions are marked with PNGAPI:
5002
5003 /* This is a public function that is visible to
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5004 * application programmers. It does thus-and-so.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5005 */
5006 void PNGAPI
5007 png_exported_function(png_ptr, png_info, foo)
5008 {
5009 body;
5010 }
5011
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5012The prototypes for all exported functions appear in png.h,
5013above the comment that says
5014
5015 /* Maintainer: Put new public prototypes here ... */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5016
5017We mark all non-exported functions with "/* PRIVATE */"":
5018
5019 void /* PRIVATE */
5020 png_non_exported_function(png_ptr, png_info, foo)
5021 {
5022 body;
5023 }
5024
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5025The prototypes for non-exported functions (except for those in
Glenn Randers-Pehrson5df7edb2009-10-29 23:32:44 -0500[diff] [blame]5026pngtest) appear in
5027pngpriv.h
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]5028above the comment that says
5029
5030 /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5031
Glenn Randers-Pehrsoncbbe9a52011-01-29 16:12:11 -0600[diff] [blame]5032To avoid polluting the global namespace, the names of all exported
5033functions and variables begin with "png_", and all publicly visible C
5034preprocessor macros begin with "PNG_". We request that applications that
5035use libpng *not* begin any of their own symbols with either of these strings.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5036
5037We put a space after each comma and after each semicolon
Glenn Randers-Pehrson49a56e72010-12-06 20:06:01 -0600[diff] [blame]5038in "for" statements, and we put spaces before and after each
Glenn Randers-Pehrsone4c706a2010-03-06 14:51:54 -0600[diff] [blame]5039C binary operator and after "for" or "while", and before
5040"?". We don't put a space between a typecast and the expression
5041being cast, nor do we put one between a function name and the
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5042left parenthesis that follows it:
5043
5044 for (i = 2; i > 0; --i)
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]5045 y[i] = a(x) + (int)b;
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5046
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]5047We prefer #ifdef and #ifndef to #if defined() and if !defined()
5048when there is only one macro being tested.
5049
Glenn Randers-Pehrson67f3b482009-09-23 11:36:28 -0500[diff] [blame]5050We do not use the TAB character for indentation in the C sources.
5051
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]5052Lines do not exceed 80 characters.
5053
Glenn Randers-Pehrsonf210a052009-11-12 10:02:24 -0600[diff] [blame]5054Other rules can be inferred by inspecting the libpng source.
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5055
Glenn Randers-Pehrson5b40b012010-11-25 07:16:29 -0600[diff] [blame]5056.SH XIV. Y2K Compliance in libpng
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]5057
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5058February 14, 2011
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5059
5060Since the PNG Development group is an ad-hoc body, we can't make
5061an official declaration.
5062
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5063This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5064upward through 1.5.2beta02 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5065versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5066
5067Libpng only has three year fields. One is a 2-byte unsigned integer that
5068will hold years up to 65535. The other two hold the date in text
5069format, and will hold years up to 9999.
5070
5071The integer is
5072 "png_uint_16 year" in png_time_struct.
5073
5074The strings are
5075 "png_charp time_buffer" in png_struct and
5076 "near_time_buffer", which is a local character string in png.c.
5077
5078There are seven time-related functions:
5079
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5080 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5081 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5082 png_convert_from_struct_tm() in pngwrite.c, called
5083 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5084 png_convert_from_time_t() in pngwrite.c
5085 png_get_tIME() in pngget.c
5086 png_handle_tIME() in pngrutil.c, called in pngread.c
5087 png_set_tIME() in pngset.c
5088 png_write_tIME() in pngwutil.c, called in pngwrite.c
5089
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5090All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5091png_convert_from_time_t() function calls gmtime() to convert from system
5092clock time, which returns (year - 1900), which we properly convert to
5093the full 4-digit year. There is a possibility that applications using
5094libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5095function, or that they are incorrectly passing only a 2-digit year
5096instead of "year - 1900" into the png_convert_from_struct_tm() function,
5097but this is not under our control. The libpng documentation has always
5098stated that it works with 4-digit years, and the APIs have been
5099documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5100
5101The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
5102integer to hold the year, and can hold years as large as 65535.
5103
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5104zlib, upon which libpng depends, is also Y2K compliant. It contains
5105no date-related code.
5106
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]5107
5108 Glenn Randers-Pehrson
5109 libpng maintainer
5110 PNG Development Group
5111
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5112.SH NOTE
5113
5114Note about libpng version numbers:
5115
5116Due to various miscommunications, unforeseen code incompatibilities
5117and occasional factors outside the authors' control, version numbering
5118on the library has not always been consistent and straightforward.
5119The following table summarizes matters since version 0.89c, which was
5120the first widely used release:
5121
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5122 source png.h png.h shared-lib
5123 version string int version
5124 ------- ------ ----- ----------
5125 0.89c ("beta 3") 0.89 89 1.0.89
5126 0.90 ("beta 4") 0.90 90 0.90
5127 0.95 ("beta 5") 0.95 95 0.95
5128 0.96 ("beta 6") 0.96 96 0.96
5129 0.97b ("beta 7") 1.00.97 97 1.0.1
5130 0.97c 0.97 97 2.0.97
5131 0.98 0.98 98 2.0.98
5132 0.99 0.99 98 2.0.99
5133 0.99a-m 0.99 99 2.0.99
5134 1.00 1.00 100 2.1.0
5135 1.0.0 1.0.0 100 2.1.0
5136 1.0.0 (from here on, the 100 2.1.0
5137 1.0.1 png.h string is 10001 2.1.0
5138 1.0.1a-e identical to the 10002 from here on, the
5139 1.0.2 source version) 10002 shared library is 2.V
5140 1.0.2a-b 10003 where V is the source
5141 1.0.1 10001 code version except as
5142 1.0.1a-e 10002 2.1.0.1a-e noted.
5143 1.0.2 10002 2.1.0.2
5144 1.0.2a-b 10003 2.1.0.2a-b
5145 1.0.3 10003 2.1.0.3
5146 1.0.3a-d 10004 2.1.0.3a-d
5147 1.0.4 10004 2.1.0.4
5148 1.0.4a-f 10005 2.1.0.4a-f
5149 1.0.5 (+ 2 patches) 10005 2.1.0.5
5150 1.0.5a-d 10006 2.1.0.5a-d
5151 1.0.5e-r 10100 2.1.0.5e-r
5152 1.0.5s-v 10006 2.1.0.5s-v
5153 1.0.6 (+ 3 patches) 10006 2.1.0.6
5154 1.0.6d-g 10007 2.1.0.6d-g
5155 1.0.6h 10007 10.6h
5156 1.0.6i 10007 10.6i
5157 1.0.6j 10007 2.1.0.6j
Glenn Randers-Pehrson25467032011-01-28 11:58:40 -0600[diff] [blame]5158 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5159 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
5160 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
5161 1.0.7 1 10007 2.1.0.7
5162 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
5163 1.0.8rc1 1 10008 2.1.0.8rc1
5164 1.0.8 1 10008 2.1.0.8
5165 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
5166 1.0.9rc1 1 10009 2.1.0.9rc1
5167 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
5168 1.0.9rc2 1 10009 2.1.0.9rc2
5169 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5170 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5171 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]5172 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]5173 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]5174 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]5175 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]5176 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
5177 1.0.12rc1 2 10012 2.1.0.12rc1
5178 1.0.12 2 10012 2.1.0.12
5179 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]5180 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrson5a0be342001-10-18 20:55:13 -0500[diff] [blame]5181 1.2.0beta3-5 3 10200 3.1.2.0beta3-5
5182 1.2.0rc1 3 10200 3.1.2.0rc1
5183 1.2.0 3 10200 3.1.2.0
Glenn Randers-Pehrson5cded0b2001-11-07 07:10:08 -0600[diff] [blame]5184 1.2.1beta-4 3 10201 3.1.2.1beta1-4
Glenn Randers-Pehrsondb3b88d2001-12-04 06:30:43 -0600[diff] [blame]5185 1.2.1rc1-2 3 10201 3.1.2.1rc1-2
5186 1.2.1 3 10201 3.1.2.1
Glenn Randers-Pehrson25228ab2002-03-31 07:33:55 -0600[diff] [blame]5187 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6
Glenn Randers-Pehrsonfcbd7872002-04-07 16:35:38 -0500[diff] [blame]5188 1.0.13beta1 10 10013 10.so.0.1.0.13beta1
5189 1.0.13rc1 10 10013 10.so.0.1.0.13rc1
5190 1.2.2rc1 12 10202 12.so.0.1.2.2rc1
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]5191 1.0.13 10 10013 10.so.0.1.0.13
5192 1.2.2 12 10202 12.so.0.1.2.2
Glenn Randers-Pehrson22f28962002-05-13 18:17:09 -0500[diff] [blame]5193 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6
5194 1.2.3 12 10203 12.so.0.1.2.3
Glenn Randers-Pehrsond020e9d2002-06-28 09:34:00 -0500[diff] [blame]5195 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3
Glenn Randers-Pehrson2ae022d2002-07-01 22:23:46 -0500[diff] [blame]5196 1.2.4rc1 13 10204 12.so.0.1.2.4rc1
Glenn Randers-Pehrson484a8a12002-07-07 19:15:20 -0500[diff] [blame]5197 1.0.14 10 10014 10.so.0.1.0.14
5198 1.2.4 13 10204 12.so.0.1.2.4
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]5199 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2
5200 1.0.15rc1 10 10015 10.so.0.1.0.15rc1
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5201 1.0.15 10 10015 10.so.0.1.0.15
5202 1.2.5 13 10205 12.so.0.1.2.5
5203 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4
Glenn Randers-Pehrson37f116a2004-08-15 07:15:39 -0500[diff] [blame]5204 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5
5205 1.0.16 10 10016 10.so.0.1.0.16
5206 1.2.6 13 10206 12.so.0.1.2.6
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]5207 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]5208 1.0.17rc1 10 10017 12.so.0.1.0.17rc1
5209 1.2.7rc1 13 10207 12.so.0.1.2.7rc1
Glenn Randers-Pehrson250dfe12004-09-11 21:19:54 -0500[diff] [blame]5210 1.0.17 10 10017 12.so.0.1.0.17
5211 1.2.7 13 10207 12.so.0.1.2.7
Glenn Randers-Pehrson40936072004-11-20 11:18:40 -0600[diff] [blame]5212 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5
Glenn Randers-Pehrson584b96e2004-11-29 15:08:00 -0600[diff] [blame]5213 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5
5214 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5
Glenn Randers-Pehrson917648e2004-12-02 18:14:51 -0600[diff] [blame]5215 1.0.18 10 10018 12.so.0.1.0.18
5216 1.2.8 13 10208 12.so.0.1.2.8
Glenn Randers-Pehrsone6474622006-03-04 16:50:47 -0600[diff] [blame]5217 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3
Glenn Randers-Pehrson4deeb792006-03-22 16:21:59 -0600[diff] [blame]5218 1.2.9beta4-11 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrson3a512032006-03-31 05:29:33 -0600[diff] [blame]5219 1.2.9rc1 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsona7d0c942006-04-14 06:22:52 -0500[diff] [blame]5220 1.2.9 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]5221 1.2.10beta1-7 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]5222 1.2.10rc1-2 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]5223 1.2.10 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]5224 1.4.0beta1-6 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]5225 1.2.11beta1-4 13 10210 12.so.0.11[.0]
Glenn Randers-Pehrson3424ee72006-07-12 13:33:47 -0500[diff] [blame]5226 1.4.0beta7-8 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrson701dbaa2006-11-17 09:36:54 -0600[diff] [blame]5227 1.2.11 13 10211 12.so.0.11[.0]
5228 1.2.12 13 10212 12.so.0.12[.0]
5229 1.4.0beta9-14 14 10400 14.so.0.0[.0]
5230 1.2.13 13 10213 12.so.0.13[.0]
Glenn Randers-Pehrson97a9b482008-10-25 20:03:28 -0500[diff] [blame]5231 1.4.0beta15-36 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsonfa028102009-10-10 06:15:21 -0500[diff] [blame]5232 1.4.0beta37-87 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson733da8c2009-10-30 00:00:15 -0500[diff] [blame]5233 1.4.0rc01 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson62ca98e2009-12-20 15:14:57 -0600[diff] [blame]5234 1.4.0beta88-109 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrson67a83db2010-01-01 18:26:18 -0600[diff] [blame]5235 1.4.0rc02-08 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsondbcfb712009-12-25 14:24:18 -0600[diff] [blame]5236 1.4.0 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsone3f3c4e2010-02-07 18:08:50 -0600[diff] [blame]5237 1.4.1beta01-03 14 10401 14.so.14.1[.0]
5238 1.4.1rc01 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson7a5be532010-02-14 07:16:19 -0600[diff] [blame]5239 1.4.1beta04-12 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrsonaaf377c2010-03-08 11:20:30 -0600[diff] [blame]5240 1.4.1 14 10401 14.so.14.1[.0]
Glenn Randers-Pehrson5b3d5542010-06-18 21:55:53 -0500[diff] [blame]5241 1.4.2 14 10402 14.so.14.2[.0]
5242 1.4.3 14 10403 14.so.14.3[.0]
Glenn Randers-Pehrson2776d5e2010-11-21 15:18:02 -0600[diff] [blame]5243 1.4.4 14 10404 14.so.14.4[.0]
Glenn Randers-Pehrsonfd20a5a2010-12-27 08:53:08 -0600[diff] [blame]5244 1.5.0beta01-58 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrson64b863c2011-01-04 09:57:06 -0600[diff] [blame]5245 1.5.0rc01-07 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrsonf5ea1b72011-01-06 06:42:51 -0600[diff] [blame]5246 1.5.0 15 10500 15.so.15.0[.0]
Glenn Randers-Pehrsonef123cc2011-01-28 15:20:34 -0600[diff] [blame]5247 1.5.1beta01-11 15 10501 15.so.15.1[.0]
Glenn Randers-Pehrson3d3aae12011-02-02 22:58:27 -0600[diff] [blame]5248 1.5.1rc01-02 15 10501 15.so.15.1[.0]
5249 1.5.1 15 10501 15.so.15.1[.0]
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5250 1.5.2beta01-02 15 10502 15.so.15.2[.0]
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5251
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5252Henceforth the source version will match the shared-library minor
5253and patch numbers; the shared-library major version number will be
5254used for changes in backward compatibility, as it is intended. The
5255PNG_PNGLIB_VER macro, which is not used within libpng but is available
5256for applications, is an unsigned integer of the form xyyzz corresponding
5257to the source version x.y.z (leading zeros in y and z). Beta versions
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]5258were given the previous public release number plus a letter, until
5259version 1.0.6j; from then on they were given the upcoming public
5260release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5261
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5262.SH "SEE ALSO"
Glenn Randers-Pehrson4e763f12010-03-03 10:45:50 -0600[diff] [blame]5263.BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5)
Glenn Randers-Pehrson7fb32a82010-03-03 09:47:49 -0600[diff] [blame]5264
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5265.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5266.IR libpng :
5267.IP
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]5268http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5269http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5270
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5271.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5272.IR zlib :
5273.IP
5274(generally) at the same location as
5275.I libpng
5276or at
5277.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5278ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5279
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5280.LP
5281.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5282.IP
5283(generally) at the same location as
5284.I libpng
5285or at
5286.br
5287ftp://ds.internic.net/rfc/rfc2083.txt
5288.br
5289or (as a W3C Recommendation) at
5290.br
5291http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5292
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]5293.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5294In the case of any inconsistency between the PNG specification
5295and this library, the specification takes precedence.
5296
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5297.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5298This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5299<glennrp at users.sourceforge.net>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5300
5301The contributing authors would like to thank all those who helped
5302with testing, bug fixes, and patience. This wouldn't have been
5303possible without all of you.
5304
5305Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]5306
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5307Libpng version 1.5.2beta02 - February 14, 2011:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5308Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5309Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5310
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5311Supported by the PNG development group
5312.br
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]5313png-mng-implement at lists.sf.net
5314(subscription required; visit
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]5315png-mng-implement at lists.sourceforge.net (subscription required; visit
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]5316https://lists.sourceforge.net/lists/listinfo/png-mng-implement
5317to subscribe).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5318
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5319.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5320
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]5321(This copy of the libpng notices is provided for your convenience. In case of
5322any discrepancy between this copy and the notices in the file png.h that is
5323included in the libpng distribution, the latter shall prevail.)
5324
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5325If you modify libpng you may insert additional notices immediately following
5326this sentence.
5327
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]5328This code is released under the libpng license.
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]5329
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5330libpng versions 1.2.6, August 15, 2004, through 1.5.2beta02, February 14, 2011, are
Glenn Randers-Pehrsona7dbcba2007-05-15 16:16:34 -0500[diff] [blame]5331Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5332distributed according to the same disclaimer and license as libpng-1.2.5
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]5333with the following individual added to the list of Contributing Authors
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5334
5335 Cosmin Truta
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]5336
5337libpng versions 1.0.7, July 1, 2000, through 1.2.5 - October 3, 2002, are
Glenn Randers-Pehrsonc6de22d2002-02-23 18:55:25 -0600[diff] [blame]5338Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]5339distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5340with the following individuals added to the list of Contributing Authors
5341
5342 Simon-Pierre Cadieux
5343 Eric S. Raymond
5344 Gilles Vollant
5345
5346and with the following additions to the disclaimer:
5347
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]5348 There is no warranty against interference with your
5349 enjoyment of the library or against infringement.
5350 There is no warranty that our efforts or the library
5351 will fulfill any of your particular purposes or needs.
5352 This library is provided with all faults, and the entire
5353 risk of satisfactory quality, performance, accuracy, and
5354 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5355
5356libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
5357Copyright (c) 1998, 1999 Glenn Randers-Pehrson
5358Distributed according to the same disclaimer and license as libpng-0.96,
5359with the following individuals added to the list of Contributing Authors:
5360
5361 Tom Lane
5362 Glenn Randers-Pehrson
5363 Willem van Schaik
5364
5365libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]5366Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5367Distributed according to the same disclaimer and license as libpng-0.88,
5368with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5369
5370 John Bowler
5371 Kevin Bracey
5372 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5373 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5374 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5375 Tom Tanner
5376
5377libpng versions 0.5, May 1995, through 0.88, January 1996, are
5378Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
5379
5380For the purposes of this copyright and license, "Contributing Authors"
5381is defined as the following set of individuals:
5382
5383 Andreas Dilger
5384 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5385 Guy Eric Schalnat
5386 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5387 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]5388
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5389The PNG Reference Library is supplied "AS IS". The Contributing Authors
5390and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5391including, without limitation, the warranties of merchantability and of
5392fitness for any purpose. The Contributing Authors and Group 42, Inc.
5393assume no liability for direct, indirect, incidental, special, exemplary,
5394or consequential damages, which may result from the use of the PNG
5395Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]5396
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5397Permission is hereby granted to use, copy, modify, and distribute this
5398source code, or portions hereof, for any purpose, without fee, subject
5399to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5400
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]54011. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5402
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]54032. Altered versions must be plainly marked as such and
5404 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5405
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]54063. This Copyright notice may not be removed or altered from
5407 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5408
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5409The Contributing Authors and Group 42, Inc. specifically permit, without
5410fee, and encourage the use of this source code as a component to
5411supporting the PNG file format in commercial products. If you use this
5412source code in a product, acknowledgment is not required but would be
5413appreciated.
5414
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5415
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5416A "png_get_copyright" function is available, for convenient use in "about"
5417boxes and the like:
5418
5419 printf("%s",png_get_copyright(NULL));
5420
5421Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]5422files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]5423
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5424Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]5425certification mark of the Open Source Initiative.
5426
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5427Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]5428glennrp at users.sourceforge.net
Glenn Randers-Pehrson93215672011-02-13 19:42:19 -0600[diff] [blame]5429February 14, 2011
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]5430
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]5431.\" end of man page
5432