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flutter / third_party / libpng / 3d893a0804f082b656d8fd8461841eb4d0aa9874 / . / libpng.3
blob: 3e47dafc0783c08a7cbb7337f96a5b5b42df53bf [file] [log] [blame]
Glenn Randers-Pehrson77d0cde2009-08-31 11:18:25 -0500[diff] [blame]1.TH LIBPNG 3 "August 31, 2009"
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]2.SH NAME
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]3libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0beta79
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
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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
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Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]19\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]21\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]23\fBint png_check_sig (png_bytep \fP\fIsig\fP\fB, int \fInum\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]24
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]25\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]27\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]28
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_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]32
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]33\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]35\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]36
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]37\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]39\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]40
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]41\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]43\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]44
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]45\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]47\fBpng_infop png_create_info_struct (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]48
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]49\fI\fB
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Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]51\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]52
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]53\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]55\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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]57\fI\fB
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Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]59\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]60
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]61\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]63\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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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]65\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]67\fBint png_debug(int \fP\fIlevel\fP\fB, png_const_charp \fImessage\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]69\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]71\fBint png_debug1(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fIp1\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]73\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]75\fBint png_debug2(int \fP\fIlevel\fP\fB, png_const_charp \fP\fImessage\fP\fB, \fP\fIp1\fP\fB, \fIp2\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]77\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]79\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]81\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]83\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]85\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]87\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]89\fI\fB
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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
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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
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]103\fBvoid png_free_default(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]105\fI\fB
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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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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]111\fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]113\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]115\fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]117\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]119\fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]121\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]123\fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]125\fI\fB
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Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]127\fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]129\fI\fB
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Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]131\fBpng_uint_32 png_get_chunk_cache_max (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]133\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]135\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]137\fI\fB
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Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]139\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]141\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]143\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]145\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]147\fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]149\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]151\fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]153\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]155\fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]157\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]159\fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]161\fI\fB
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Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]163\fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]165\fI\fB
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Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]167\fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]169\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]171\fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]173\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]175\fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]177\fI\fB
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Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]179\fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]180
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]181\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]183\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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]185\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]187\fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]189\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]191\fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]193\fI\fB
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195\fB#if \fI!defined(PNG_1_0_X)
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197\fBpng_int_32 png_get_int_32 (png_bytep \fIbuf\fP\fB);\fP
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199\fI\fB#endif
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201\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]202
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]203\fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]205\fI\fB
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Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]207\fBpng_voidp png_get_io_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]209\fI\fB
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Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]211\fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP
212
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]213\fI\fB
214
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]215\fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP
216
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]217\fI\fB
218
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]219\fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_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
220
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]221\fI\fB
222
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]223\fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_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
224
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]225\fI\fB
226
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]227\fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_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
228
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]229\fI\fB
230
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]231\fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
232
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]233\fI\fB
234
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]235\fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
236
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]237\fI\fB
238
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]239\fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP
240
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]241\fI\fB
242
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]243\fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP
244
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]245\fI\fB
246
247\fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr)
248
249\fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
250
251\fI\fB
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]252
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]253\fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
254
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]255\fI\fB
256
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]257\fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]259\fI\fB
260
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]261\fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
262
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]263\fI\fB
264
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]265\fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_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]266
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]267\fI\fB
268
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]269\fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]271\fI\fB
272
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]273\fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]275\fI\fB
276
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]277\fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]279\fI\fB
280
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]281\fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\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]282
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]283\fI\fB
284
285\fB/* This function is really an inline macro. \fI*/
286
287\fBpng_uint_16 png_get_uint_16 (png_bytep \fIbuf\fP\fB);\fP
288
289\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]290
291\fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP
292
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]293\fI\fB
294
295\fB/* This function is really an inline macro. \fI*/
296
297\fBpng_uint_32 png_get_uint_32 (png_bytep \fIbuf\fP\fB);\fP
298
299\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]300
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]301\fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]303\fI\fB
304
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]305\fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]307\fI\fB
308
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]309\fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]311\fI\fB
312
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]313\fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]315\fI\fB
316
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]317\fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]319\fI\fB
320
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]321\fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]323\fI\fB
324
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]325\fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]326
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]327\fI\fB
328
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]329\fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]330
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]331\fI\fB
332
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]333\fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]335\fI\fB
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Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]337\fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]338
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]339\fI\fB
340
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]341\fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]342
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]343\fI\fB
344
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]345\fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]347\fI\fB
348
Glenn Randers-Pehrsonc1bfe682002-03-06 22:08:00 -0600[diff] [blame]349\fBint png_handle_as_unknown (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIchunk_name\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]351\fI\fB
352
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]353\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]354
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]355\fI\fB
356
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]357\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]358
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]359\fI\fB
360
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]361\fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]362
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]363\fI\fB
364
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]365\fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]367\fI\fB
368
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]369\fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]371\fI\fB
372
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]373\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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]375\fI\fB
376
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]377\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
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]379\fI\fB
380
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]381\fBvoid png_read_destroy (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_infop \fIend_info_ptr\fP\fB);\fP
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Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]383\fI\fB
384
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]385\fBvoid png_read_end (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
386
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]387\fI\fB
388
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]389\fBvoid png_read_image (png_structp \fP\fIpng_ptr\fP\fB, png_bytepp \fIimage\fP\fB);\fP
390
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]391\fI\fB
392
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]393\fBvoid png_read_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
394
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]395\fI\fB
396
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]397\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]398
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]399\fI\fB
400
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]401\fBvoid png_read_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIrow\fP\fB, png_bytep \fIdisplay_row\fP\fB);\fP
402
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]403\fI\fB
404
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]405\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
406
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]407\fI\fB
408
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]409\fBvoid png_read_update_info (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
410
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]411\fI\fB
412
413\fB#if \fI!defined(PNG_1_0_X)
414
415\fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP
416
417\fI\fB
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]418
419\fBvoid png_save_uint_16 (png_bytep \fP\fIbuf\fP\fB, unsigned int \fIi\fP\fB);\fP
420
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]421\fI\fB
422
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]423\fBvoid png_save_uint_32 (png_bytep \fP\fIbuf\fP\fB, png_uint_32 \fIi\fP\fB);\fP
424
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]425\fI\fB
426
427\fBvoid png_set_add_alpha (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIfiller\fP\fB, int \fIflags\fP\fB);\fP
428
429\fI\fB#endif
430
431\fI\fB
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]432
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]433\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
434
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]435\fI\fB
436
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]437\fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP
438
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]439\fI\fB
440
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]441\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
442
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]443\fI\fB
444
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]445\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
446
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]447\fI\fB
448
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]449\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
450
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]451\fI\fB
452
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]453\fBvoid png_set_chunk_cache_max (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIuser_chunk_cache_max\fP\fB);\fP
454
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]455\fI\fB
456
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]457\fBvoid png_set_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP
458
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]459\fI\fB
460
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]461\fBvoid png_set_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP
462
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]463\fI\fB
464
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]465\fBvoid png_set_compression_method (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod\fP\fB);\fP
466
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]467\fI\fB
468
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]469\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]470
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]471\fI\fB
472
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]473\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]474
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]475\fI\fB
476
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]477\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]478
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]479\fI\fB
480
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]481\fBvoid png_set_dither (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_dither\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]482
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]483\fI\fB
484
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]485\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]486
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]487\fI\fB
488
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]489\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]490
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]491\fI\fB
492
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]493\fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP
494
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]495\fI\fB
496
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]497\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]498
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]499\fI\fB
500
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]501\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]502
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]503\fI\fB
504
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]505\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]506
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]507\fI\fB
508
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]509\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]510
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]511\fI\fB
512
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]513\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]514
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]515\fI\fB
516
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]517\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]518
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]519\fI\fB
520
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]521\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
522
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]523\fI\fB
524
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]525\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]526
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]527\fI\fB
528
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]529\fBvoid png_set_gray_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]530
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]531\fI\fB
532
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]533\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]534
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]535\fI\fB
536
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]537\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]538
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]539\fI\fB
540
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]541\fBint png_set_interlace_handling (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]542
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]543\fI\fB
544
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]545\fBvoid png_set_invalid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fImask\fP\fB);\fP
546
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]547\fI\fB
548
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]549\fBvoid png_set_invert_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]550
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]551\fI\fB
552
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]553\fBvoid png_set_invert_mono (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]554
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]555\fI\fB
556
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]557\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]558
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]559\fI\fB
560
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]561\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]562
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]563\fI\fB
564
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]565\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]566
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]567\fI\fB
568
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]569\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]570
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]571\fI\fB
572
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]573\fBvoid png_set_packing (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]574
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]575\fI\fB
576
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]577\fBvoid png_set_packswap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]578
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]579\fI\fB
580
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]581\fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]582
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]583\fI\fB
584
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]585\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]586
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]587\fI\fB
588
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]589\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]590
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]591\fI\fB
592
Glenn Randers-Pehrson1916f6a2008-08-14 13:44:49 -0500[diff] [blame]593\fBvoid png_set_premultiply_alpha (png_structp \fIpng_ptr\fP\fB);\fP
594
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]595\fI\fB
596
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]597\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]598
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]599\fI\fB
600
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]601\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]602
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]603\fI\fB
604
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]605\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]606
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]607\fI\fB
608
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]609\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]610
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]611\fI\fB
612
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]613\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]614
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]615\fI\fB
616
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]617\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
618
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]619\fI\fB
620
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]621\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]622
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]623\fI\fB
624
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]625\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
626
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]627\fI\fB
628
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]629\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]630
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]631\fI\fB
632
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]633\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP
634
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]635\fI\fB
636
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]637\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]638
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]639\fI\fB
640
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]641\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]642
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]643\fI\fB
644
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]645\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]646
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]647\fI\fB
648
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]649\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]650
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]651\fI\fB
652
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]653\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]654
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]655\fI\fB
656
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]657\fBvoid png_set_strip_16 (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]658
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]659\fI\fB
660
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]661\fBvoid png_set_strip_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]662
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]663\fI\fB
664
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]665\fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]666
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]667\fI\fB
668
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]669\fBvoid png_set_swap_alpha (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]670
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]671\fI\fB
672
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]673\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]674
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]675\fI\fB
676
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]677\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]678
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]679\fI\fB
680
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]681\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\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]682
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]683\fI\fB
684
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]685\fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]686
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]687\fI\fB
688
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]689\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
690
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]691\fI\fB
692
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]693\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
694
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]695\fI\fB
696
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]697\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
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]698
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]699\fI\fB
700
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]701\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
702
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]703\fI\fB
704
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]705\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]706
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]707\fI\fB
708
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]709\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]710
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]711\fI\fB
712
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]713\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]714
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]715\fI\fB
716
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]717\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]718
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]719\fI\fB
720
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]721\fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP
722
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]723\fI\fB
724
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]725\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]726
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]727\fI\fB
728
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]729\fBvoid png_start_read_image (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]730
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]731\fI\fB
732
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]733\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]734
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]735\fI\fB
736
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]737\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]738
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]739\fI\fB
740
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]741\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]742
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]743\fI\fB
744
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]745\fBvoid png_write_chunk_end (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]746
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]747\fI\fB
748
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]749\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]750
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]751\fI\fB
752
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]753\fBvoid png_write_destroy (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]754
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]755\fI\fB
756
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]757\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]758
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]759\fI\fB
760
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]761\fBvoid png_write_flush (png_structp \fIpng_ptr\fP\fB);\fP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]762
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]763\fI\fB
764
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]765\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]766
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]767\fI\fB
768
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]769\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]770
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]771\fI\fB
772
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]773\fBvoid png_write_info_before_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP
774
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]775\fI\fB
776
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]777\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]778
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]779\fI\fB
780
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]781\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]782
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]783\fI\fB
784
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]785\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]786
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]787\fI\fB
788
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]789\fBvoid png_write_sig (png_structp \fIpng_ptr\fP\fB);\fP
790
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]791\fI\fB
792
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]793\fBvoidpf png_zalloc (voidpf \fP\fIpng_ptr\fP\fB, uInt \fP\fIitems\fP\fB, uInt \fIsize\fP\fB);\fP
794
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]795\fI\fB
796
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]797\fBvoid png_zfree (voidpf \fP\fIpng_ptr\fP\fB, voidpf \fIptr\fP\fB);\fP
798
Glenn Randers-Pehrsonad81d712009-07-30 15:39:00 -0500[diff] [blame]799\fI\fB
800
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]801.SH DESCRIPTION
802The
803.I libpng
804library supports encoding, decoding, and various manipulations of
805the Portable Network Graphics (PNG) format image files. It uses the
806.IR zlib(3)
807compression library.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]808Following is a copy of the libpng.txt file that accompanies libpng.
809.SH LIBPNG.TXT
810libpng.txt - A description on how to use and modify libpng
811
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]812 libpng version 1.4.0beta79 - August 31, 2009
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]813 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]814 <glennrp at users.sourceforge.net>
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]815 Copyright (c) 1998-2009 Glenn Randers-Pehrson
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]816
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]817 This document is released under the libpng license.
Glenn Randers-Pehrsonc332bbc2009-06-25 13:43:50 -0500[diff] [blame]818 For conditions of distribution and use, see the disclaimer
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]819 and license in png.h
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]820
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]821 Based on:
822
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]823 libpng versions 0.97, January 1998, through 1.4.0beta79 - August 31, 2009
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]824 Updated and distributed by Glenn Randers-Pehrson
Glenn Randers-Pehrsona93c9422009-04-13 11:41:33 -0500[diff] [blame]825 Copyright (c) 1998-2009 Glenn Randers-Pehrson
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]826
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]827 libpng 1.0 beta 6 version 0.96 May 28, 1997
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]828 Updated and distributed by Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]829 Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]830
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]831 libpng 1.0 beta 2 - version 0.88 January 26, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]832 For conditions of distribution and use, see copyright
833 notice in png.h. Copyright (c) 1995, 1996 Guy Eric
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]834 Schalnat, Group 42, Inc.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]835
836 Updated/rewritten per request in the libpng FAQ
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]837 Copyright (c) 1995, 1996 Frank J. T. Wojcik
838 December 18, 1995 & January 20, 1996
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]839
840.SH I. Introduction
841
842This file describes how to use and modify the PNG reference library
843(known as libpng) for your own use. There are five sections to this
844file: introduction, structures, reading, writing, and modification and
845configuration notes for various special platforms. In addition to this
846file, example.c is a good starting point for using the library, as
847it is heavily commented and should include everything most people
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]848will need. We assume that libpng is already installed; see the
849INSTALL file for instructions on how to install libpng.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]850
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]851For examples of libpng usage, see the files "example.c", "pngtest.c",
852and the files in the "contrib" directory, all of which are included in the
853libpng distribution.
854
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]855Libpng was written as a companion to the PNG specification, as a way
856of reducing the amount of time and effort it takes to support the PNG
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]857file format in application programs.
858
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]859The PNG specification (second edition), November 2003, is available as
860a W3C Recommendation and as an ISO Standard (ISO/IEC 15948:2003 (E)) at
861<http://www.w3.org/TR/2003/REC-PNG-20031110/
862The W3C and ISO documents have identical technical content.
863
864The PNG-1.2 specification is available at
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]865<http://www.libpng.org/pub/png/documents/>. It is technically equivalent
866to the PNG specification (second edition) but has some additional material.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]867
868The PNG-1.0 specification is available
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]869as RFC 2083 <http://www.libpng.org/pub/png/documents/> and as a
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]870W3C Recommendation <http://www.w3.org/TR/REC.png.html>.
871
872Some additional chunks are described in the special-purpose public chunks
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]873documents at <http://www.libpng.org/pub/png/documents/>.
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]874
875Other information
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]876about 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]877page, <http://www.libpng.org/pub/png/>.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]878
879Most users will not have to modify the library significantly; advanced
880users may want to modify it more. All attempts were made to make it as
881complete as possible, while keeping the code easy to understand.
882Currently, this library only supports C. Support for other languages
883is being considered.
884
885Libpng has been designed to handle multiple sessions at one time,
886to be easily modifiable, to be portable to the vast majority of
887machines (ANSI, K&R, 16-, 32-, and 64-bit) available, and to be easy
888to use. The ultimate goal of libpng is to promote the acceptance of
889the PNG file format in whatever way possible. While there is still
890work to be done (see the TODO file), libpng should cover the
891majority of the needs of its users.
892
893Libpng uses zlib for its compression and decompression of PNG files.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]894Further information about zlib, and the latest version of zlib, can
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]895be 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]896The zlib compression utility is a general purpose utility that is
897useful for more than PNG files, and can be used without libpng.
898See the documentation delivered with zlib for more details.
899You can usually find the source files for the zlib utility wherever you
900find the libpng source files.
901
902Libpng is thread safe, provided the threads are using different
903instances of the structures. Each thread should have its own
904png_struct and png_info instances, and thus its own image.
905Libpng does not protect itself against two threads using the
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]906same instance of a structure.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]907
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]908.SH II. Structures
909
910There are two main structures that are important to libpng, png_struct
911and png_info. The first, png_struct, is an internal structure that
912will not, for the most part, be used by a user except as the first
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]913variable passed to every libpng function call.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]914
915The png_info structure is designed to provide information about the
916PNG file. At one time, the fields of png_info were intended to be
917directly accessible to the user. However, this tended to cause problems
918with applications using dynamically loaded libraries, and as a result
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]919a set of interface functions for png_info (the png_get_*() and png_set_*()
920functions) was developed. The fields of png_info are still available for
921older applications, but it is suggested that applications use the new
922interfaces if at all possible.
923
924Applications that do make direct access to the members of png_struct (except
925for png_ptr->jmpbuf) must be recompiled whenever the library is updated,
926and applications that make direct access to the members of png_info must
927be recompiled if they were compiled or loaded with libpng version 1.0.6,
928in which the members were in a different order. In version 1.0.7, the
929members of the png_info structure reverted to the old order, as they were
930in versions 0.97c through 1.0.5. Starting with version 2.0.0, both
931structures are going to be hidden, and the contents of the structures will
932only be accessible through the png_get/png_set functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]933
934The png.h header file is an invaluable reference for programming with libpng.
935And while I'm on the topic, make sure you include the libpng header file:
936
937#include <png.h>
938
939.SH III. Reading
940
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]941We'll now walk you through the possible functions to call when reading
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]942in a PNG file sequentially, briefly explaining the syntax and purpose
943of each one. See example.c and png.h for more detail. While
944progressive reading is covered in the next section, you will still
945need some of the functions discussed in this section to read a PNG
946file.
947
948.SS Setup
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]949
950You will want to do the I/O initialization(*) before you get into libpng,
951so if it doesn't work, you don't have much to undo. Of course, you
952will also want to insure that you are, in fact, dealing with a PNG
953file. 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]954To 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]955png_sig_cmp(), and it will return 0 (false) if the bytes match the
956corresponding bytes of the PNG signature, or nonzero (true) otherwise.
957Of course, the more bytes you pass in, the greater the accuracy of the
958prediction.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]959
960If you are intending to keep the file pointer open for use in libpng,
961you must ensure you don't read more than 8 bytes from the beginning
962of the file, and you also have to make a call to png_set_sig_bytes_read()
963with the number of bytes you read from the beginning. Libpng will
964then only check the bytes (if any) that your program didn't read.
965
966(*): If you are not using the standard I/O functions, you will need
967to replace them with custom functions. See the discussion under
968Customizing libpng.
969
970
971 FILE *fp = fopen(file_name, "rb");
972 if (!fp)
973 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]974 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]975 }
976 fread(header, 1, number, fp);
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]977 is_png = !png_sig_cmp(header, 0, number);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]978 if (!is_png)
979 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]980 return (NOT_PNG);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]981 }
982
983
984Next, png_struct and png_info need to be allocated and initialized. In
985order to ensure that the size of these structures is correct even with a
986dynamically linked libpng, there are functions to initialize and
987allocate the structures. We also pass the library version, optional
988pointers to error handling functions, and a pointer to a data struct for
989use by the error functions, if necessary (the pointer and functions can
990be NULL if the default error handlers are to be used). See the section
991on Changes to Libpng below regarding the old initialization functions.
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]992The structure allocation functions quietly return NULL if they fail to
993create the structure, so your application should check for that.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]994
995 png_structp png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]996 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]997 user_error_fn, user_warning_fn);
998 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]999 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1000
1001 png_infop info_ptr = png_create_info_struct(png_ptr);
1002 if (!info_ptr)
1003 {
1004 png_destroy_read_struct(&png_ptr,
1005 (png_infopp)NULL, (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1006 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1007 }
1008
1009 png_infop end_info = png_create_info_struct(png_ptr);
1010 if (!end_info)
1011 {
1012 png_destroy_read_struct(&png_ptr, &info_ptr,
1013 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1014 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1015 }
1016
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1017If you want to use your own memory allocation routines,
1018define PNG_USER_MEM_SUPPORTED and use
1019png_create_read_struct_2() instead of png_create_read_struct():
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1020
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]1021 png_structp png_ptr = png_create_read_struct_2
1022 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
1023 user_error_fn, user_warning_fn, (png_voidp)
1024 user_mem_ptr, user_malloc_fn, user_free_fn);
1025
1026The error handling routines passed to png_create_read_struct()
1027and the memory alloc/free routines passed to png_create_struct_2()
1028are only necessary if you are not using the libpng supplied error
1029handling and memory alloc/free functions.
1030
1031When libpng encounters an error, it expects to longjmp back
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1032to your routine. Therefore, you will need to call setjmp and pass
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1033your png_jmpbuf(png_ptr). If you read the file from different
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1034routines, you will need to update the jmpbuf field every time you enter
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1035a new routine that will call a png_*() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1036
1037See your documentation of setjmp/longjmp for your compiler for more
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1038information on setjmp/longjmp. See the discussion on libpng error
1039handling in the Customizing Libpng section below for more information
1040on the libpng error handling. If an error occurs, and libpng longjmp's
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1041back to your setjmp, you will want to call png_destroy_read_struct() to
1042free any memory.
1043
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1044 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1045 {
1046 png_destroy_read_struct(&png_ptr, &info_ptr,
1047 &end_info);
1048 fclose(fp);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]1049 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1050 }
1051
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1052If you would rather avoid the complexity of setjmp/longjmp issues,
1053you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
1054errors will result in a call to PNG_ABORT() which defaults to abort().
1055
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1056Now you need to set up the input code. The default for libpng is to
1057use the C function fread(). If you use this, you will need to pass a
1058valid FILE * in the function png_init_io(). Be sure that the file is
1059opened in binary mode. If you wish to handle reading data in another
1060way, you need not call the png_init_io() function, but you must then
1061implement the libpng I/O methods discussed in the Customizing Libpng
1062section below.
1063
1064 png_init_io(png_ptr, fp);
1065
1066If you had previously opened the file and read any of the signature from
1067the beginning in order to see if this was a PNG file, you need to let
1068libpng know that there are some bytes missing from the start of the file.
1069
1070 png_set_sig_bytes(png_ptr, number);
1071
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1072.SS Setting up callback code
1073
1074You can set up a callback function to handle any unknown chunks in the
1075input stream. You must supply the function
1076
1077 read_chunk_callback(png_ptr ptr,
1078 png_unknown_chunkp chunk);
1079 {
1080 /* The unknown chunk structure contains your
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1081 chunk data, along with similar data for any other
1082 unknown chunks: */
1083
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1084 png_byte name[5];
1085 png_byte *data;
1086 png_size_t size;
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1087
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1088 /* Note that libpng has already taken care of
1089 the CRC handling */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1090
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1091 /* put your code here. Search for your chunk in the
1092 unknown chunk structure, process it, and return one
1093 of the following: */
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1094
1095 return (-n); /* chunk had an error */
1096 return (0); /* did not recognize */
1097 return (n); /* success */
1098 }
1099
1100(You can give your function another name that you like instead of
1101"read_chunk_callback")
1102
1103To inform libpng about your function, use
1104
1105 png_set_read_user_chunk_fn(png_ptr, user_chunk_ptr,
1106 read_chunk_callback);
1107
1108This names not only the callback function, but also a user pointer that
1109you can retrieve with
1110
1111 png_get_user_chunk_ptr(png_ptr);
1112
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1113If you call the png_set_read_user_chunk_fn() function, then all unknown
1114chunks will be saved when read, in case your callback function will need
1115one or more of them. This behavior can be changed with the
1116png_set_keep_unknown_chunks() function, described below.
1117
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1118At this point, you can set up a callback function that will be
1119called after each row has been read, which you can use to control
1120a progress meter or the like. It's demonstrated in pngtest.c.
1121You must supply a function
1122
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]1123 void read_row_callback(png_ptr ptr, png_uint_32 row,
1124 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]1125 {
1126 /* put your code here */
1127 }
1128
1129(You can give it another name that you like instead of "read_row_callback")
1130
1131To inform libpng about your function, use
1132
1133 png_set_read_status_fn(png_ptr, read_row_callback);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1134
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1135.SS Unknown-chunk handling
1136
1137Now you get to set the way the library processes unknown chunks in the
1138input PNG stream. Both known and unknown chunks will be read. Normal
1139behavior is that known chunks will be parsed into information in
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1140various info_ptr members while unknown chunks will be discarded. This
1141behavior can be wasteful if your application will never use some known
1142chunk types. To change this, you can call:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1143
Glenn Randers-Pehrson272489d2004-08-04 06:34:52 -0500[diff] [blame]1144 png_set_keep_unknown_chunks(png_ptr, keep,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1145 chunk_list, num_chunks);
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1146 keep - 0: default unknown chunk handling
1147 1: ignore; do not keep
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1148 2: keep only if safe-to-copy
1149 3: keep even if unsafe-to-copy
1150 You can use these definitions:
1151 PNG_HANDLE_CHUNK_AS_DEFAULT 0
1152 PNG_HANDLE_CHUNK_NEVER 1
1153 PNG_HANDLE_CHUNK_IF_SAFE 2
1154 PNG_HANDLE_CHUNK_ALWAYS 3
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1155 chunk_list - list of chunks affected (a byte string,
1156 five bytes per chunk, NULL or '\0' if
1157 num_chunks is 0)
1158 num_chunks - number of chunks affected; if 0, all
Glenn Randers-Pehrsondff799e2004-08-07 21:42:49 -0500[diff] [blame]1159 unknown chunks are affected. If nonzero,
1160 only the chunks in the list are affected
1161
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1162Unknown chunks declared in this way will be saved as raw data onto a
1163list of png_unknown_chunk structures. If a chunk that is normally
1164known to libpng is named in the list, it will be handled as unknown,
1165according to the "keep" directive. If a chunk is named in successive
1166instances of png_set_keep_unknown_chunks(), the final instance will
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]1167take precedence. The IHDR and IEND chunks should not be named in
1168chunk_list; if they are, libpng will process them normally anyway.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1169
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1170Here is an example of the usage of png_set_keep_unknown_chunks(),
1171where the private "vpAg" chunk will later be processed by a user chunk
1172callback function:
1173
1174 png_byte vpAg[5]={118, 112, 65, 103, (png_byte) '\0'};
1175
1176 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1177 png_byte unused_chunks[]=
1178 {
1179 104, 73, 83, 84, (png_byte) '\0', /* hIST */
1180 105, 84, 88, 116, (png_byte) '\0', /* iTXt */
1181 112, 67, 65, 76, (png_byte) '\0', /* pCAL */
1182 115, 67, 65, 76, (png_byte) '\0', /* sCAL */
1183 115, 80, 76, 84, (png_byte) '\0', /* sPLT */
1184 116, 73, 77, 69, (png_byte) '\0', /* tIME */
1185 };
1186 #endif
1187
1188 ...
1189
1190 #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED)
1191 /* ignore all unknown chunks: */
1192 png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0);
1193 /* except for vpAg: */
1194 png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1);
1195 /* also ignore unused known chunks: */
1196 png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks,
1197 (int)sizeof(unused_chunks)/5);
1198 #endif
1199
Glenn Randers-Pehrson800d1e92008-08-20 17:25:21 -0500[diff] [blame]1200.SS User limits
1201
1202The PNG specification allows the width and height of an image to be as
1203large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns.
1204Since very few applications really need to process such large images,
1205we have imposed an arbitrary 1-million limit on rows and columns.
1206Larger images will be rejected immediately with a png_error() call. If
1207you wish to override this limit, you can use
1208
1209 png_set_user_limits(png_ptr, width_max, height_max);
1210
1211to set your own limits, or use width_max = height_max = 0x7fffffffL
1212to allow all valid dimensions (libpng may reject some very large images
1213anyway because of potential buffer overflow conditions).
1214
1215You should put this statement after you create the PNG structure and
1216before calling png_read_info(), png_read_png(), or png_process_data().
1217If you need to retrieve the limits that are being applied, use
1218
1219 width_max = png_get_user_width_max(png_ptr);
1220 height_max = png_get_user_height_max(png_ptr);
1221
1222The PNG specification sets no limit on the number of ancillary chunks
1223allowed in a PNG datastream. You can impose a limit on the total number
1224of sPLT, tEXt, iTXt, zTXt, and unknown chunks that will be stored, with
1225
1226 png_set_chunk_cache_max(png_ptr, user_chunk_cache_max);
1227
1228where 0x7fffffffL means unlimited. You can retrieve this limit with
1229
1230 chunk_cache_max = png_get_chunk_cache_max(png_ptr);
1231
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1232.SS The high-level read interface
1233
1234At this point there are two ways to proceed; through the high-level
1235read interface, or through a sequence of low-level read operations.
1236You can use the high-level interface if (a) you are willing to read
1237the entire image into memory, and (b) the input transformations
1238you want to do are limited to the following set:
1239
1240 PNG_TRANSFORM_IDENTITY No transformation
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1241 PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to
1242 8 bits
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1243 PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1244 PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit
1245 samples to bytes
1246 PNG_TRANSFORM_PACKSWAP Change order of packed
1247 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1248 PNG_TRANSFORM_EXPAND Perform set_expand()
1249 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1250 PNG_TRANSFORM_SHIFT Normalize pixels to the
1251 sBIT depth
1252 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
1253 to BGRA
1254 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
1255 to AG
1256 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
1257 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1258 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]1259 PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples
1260 to RGB (or GA to RGBA)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1261
1262(This excludes setting a background color, doing gamma transformation,
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1263dithering, and setting filler.) If this is the case, simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1264
1265 png_read_png(png_ptr, info_ptr, png_transforms, NULL)
1266
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]1267where png_transforms is an integer containing the bitwise OR of
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1268some set of transformation flags. This call is equivalent to png_read_info(),
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1269followed the set of transformations indicated by the transform mask,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1270then png_read_image(), and finally png_read_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1271
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1272(The final parameter of this call is not yet used. Someday it might point
1273to transformation parameters required by some future input transform.)
1274
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]1275You must use png_transforms and not call any png_set_transform() functions
1276when you use png_read_png().
1277
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1278After you have called png_read_png(), you can retrieve the image data
1279with
1280
1281 row_pointers = png_get_rows(png_ptr, info_ptr);
1282
1283where row_pointers is an array of pointers to the pixel data for each row:
1284
1285 png_bytep row_pointers[height];
1286
1287If you know your image size and pixel size ahead of time, you can allocate
1288row_pointers prior to calling png_read_png() with
1289
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1290 if (height > PNG_UINT_32_MAX/png_sizeof(png_byte))
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]1291 png_error (png_ptr,
1292 "Image is too tall to process in memory");
1293 if (width > PNG_UINT_32_MAX/pixel_size)
1294 png_error (png_ptr,
1295 "Image is too wide to process in memory");
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1296 row_pointers = png_malloc(png_ptr,
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1297 height*png_sizeof(png_bytep));
1298 for (int i=0; i<height, i++)
1299 row_pointers[i]=NULL; /* security precaution */
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1300 for (int i=0; i<height, i++)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1301 row_pointers[i]=png_malloc(png_ptr,
1302 width*pixel_size);
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]1303 png_set_rows(png_ptr, info_ptr, &row_pointers);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]1304
1305Alternatively you could allocate your image in one big block and define
1306row_pointers[i] to point into the proper places in your block.
1307
1308If you use png_set_rows(), the application is responsible for freeing
1309row_pointers (and row_pointers[i], if they were separately allocated).
1310
1311If you don't allocate row_pointers ahead of time, png_read_png() will
1312do it, and it'll be free'ed when you call png_destroy_*().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1313
1314.SS The low-level read interface
1315
1316If you are going the low-level route, you are now ready to read all
1317the file information up to the actual image data. You do this with a
1318call to png_read_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1319
1320 png_read_info(png_ptr, info_ptr);
1321
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1322This will process all chunks up to but not including the image data.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1323
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1324.SS Querying the info structure
1325
1326Functions are used to get the information from the info_ptr once it
1327has been read. Note that these fields may not be completely filled
1328in until png_read_end() has read the chunk data following the image.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1329
1330 png_get_IHDR(png_ptr, info_ptr, &width, &height,
1331 &bit_depth, &color_type, &interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1332 &compression_type, &filter_method);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1333
1334 width - holds the width of the image
1335 in pixels (up to 2^31).
1336 height - holds the height of the image
1337 in pixels (up to 2^31).
1338 bit_depth - holds the bit depth of one of the
1339 image channels. (valid values are
1340 1, 2, 4, 8, 16 and depend also on
1341 the color_type. See also
1342 significant bits (sBIT) below).
1343 color_type - describes which color/alpha channels
1344 are present.
1345 PNG_COLOR_TYPE_GRAY
1346 (bit depths 1, 2, 4, 8, 16)
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1347 PNG_COLOR_TYPE_GRAY_ALPHA
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1348 (bit depths 8, 16)
1349 PNG_COLOR_TYPE_PALETTE
1350 (bit depths 1, 2, 4, 8)
1351 PNG_COLOR_TYPE_RGB
1352 (bit_depths 8, 16)
1353 PNG_COLOR_TYPE_RGB_ALPHA
1354 (bit_depths 8, 16)
1355
1356 PNG_COLOR_MASK_PALETTE
1357 PNG_COLOR_MASK_COLOR
1358 PNG_COLOR_MASK_ALPHA
1359
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1360 filter_method - (must be PNG_FILTER_TYPE_BASE
1361 for PNG 1.0, and can also be
1362 PNG_INTRAPIXEL_DIFFERENCING if
1363 the PNG datastream is embedded in
1364 a MNG-1.0 datastream)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1365 compression_type - (must be PNG_COMPRESSION_TYPE_BASE
1366 for PNG 1.0)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1367 interlace_type - (PNG_INTERLACE_NONE or
1368 PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1369 Any or all of interlace_type, compression_type, of
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1370 filter_method can be NULL if you are
1371 not interested in their values.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1372
1373 channels = png_get_channels(png_ptr, info_ptr);
1374 channels - number of channels of info for the
1375 color type (valid values are 1 (GRAY,
1376 PALETTE), 2 (GRAY_ALPHA), 3 (RGB),
1377 4 (RGB_ALPHA or RGB + filler byte))
1378 rowbytes = png_get_rowbytes(png_ptr, info_ptr);
1379 rowbytes - number of bytes needed to hold a row
1380
1381 signature = png_get_signature(png_ptr, info_ptr);
1382 signature - holds the signature read from the
1383 file (if any). The data is kept in
1384 the same offset it would be if the
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1385 whole signature were read (i.e. if an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1386 application had already read in 4
1387 bytes of signature before starting
1388 libpng, the remaining 4 bytes would
1389 be in signature[4] through signature[7]
1390 (see png_set_sig_bytes())).
1391
1392
1393 width = png_get_image_width(png_ptr,
1394 info_ptr);
1395 height = png_get_image_height(png_ptr,
1396 info_ptr);
1397 bit_depth = png_get_bit_depth(png_ptr,
1398 info_ptr);
1399 color_type = png_get_color_type(png_ptr,
1400 info_ptr);
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]1401 filter_method = png_get_filter_type(png_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1402 info_ptr);
1403 compression_type = png_get_compression_type(png_ptr,
1404 info_ptr);
1405 interlace_type = png_get_interlace_type(png_ptr,
1406 info_ptr);
1407
1408
1409These are also important, but their validity depends on whether the chunk
1410has been read. The png_get_valid(png_ptr, info_ptr, PNG_INFO_<chunk>) and
1411png_get_<chunk>(png_ptr, info_ptr, ...) functions return non-zero if the
1412data has been read, or zero if it is missing. The parameters to the
1413png_get_<chunk> are set directly if they are simple data types, or a pointer
1414into the info_ptr is returned for any complex types.
1415
1416 png_get_PLTE(png_ptr, info_ptr, &palette,
1417 &num_palette);
1418 palette - the palette for the file
1419 (array of png_color)
1420 num_palette - number of entries in the palette
1421
1422 png_get_gAMA(png_ptr, info_ptr, &gamma);
1423 gamma - the gamma the file is written
1424 at (PNG_INFO_gAMA)
1425
1426 png_get_sRGB(png_ptr, info_ptr, &srgb_intent);
1427 srgb_intent - the rendering intent (PNG_INFO_sRGB)
1428 The presence of the sRGB chunk
1429 means that the pixel data is in the
1430 sRGB color space. This chunk also
1431 implies specific values of gAMA and
1432 cHRM.
1433
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1434 png_get_iCCP(png_ptr, info_ptr, &name,
1435 &compression_type, &profile, &proflen);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1436 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1437 compression - The compression type; always
1438 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
1439 You may give NULL to this argument to
1440 ignore it.
1441 profile - International Color Consortium color
1442 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1443 proflen - length of profile data in bytes.
1444
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1445 png_get_sBIT(png_ptr, info_ptr, &sig_bit);
1446 sig_bit - the number of significant bits for
1447 (PNG_INFO_sBIT) each of the gray,
1448 red, green, and blue channels,
1449 whichever are appropriate for the
1450 given color type (png_color_16)
1451
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]1452 png_get_tRNS(png_ptr, info_ptr, &trans_alpha,
1453 &num_trans, &trans_color);
1454 trans_alpha - array of alpha (transparency)
1455 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]1456 trans_color - graylevel or color sample values of
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]1457 the single transparent color for
1458 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1459 num_trans - number of transparent entries
1460 (PNG_INFO_tRNS)
1461
1462 png_get_hIST(png_ptr, info_ptr, &hist);
1463 (PNG_INFO_hIST)
1464 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1465 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1466
1467 png_get_tIME(png_ptr, info_ptr, &mod_time);
1468 mod_time - time image was last modified
1469 (PNG_VALID_tIME)
1470
1471 png_get_bKGD(png_ptr, info_ptr, &background);
1472 background - background color (PNG_VALID_bKGD)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1473 valid 16-bit red, green and blue
1474 values, regardless of color_type
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1475
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]1476 num_comments = png_get_text(png_ptr, info_ptr,
1477 &text_ptr, &num_text);
1478 num_comments - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1479 text_ptr - array of png_text holding image
1480 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1481 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1482 on "text" PNG_TEXT_COMPRESSION_NONE
1483 PNG_TEXT_COMPRESSION_zTXt
1484 PNG_ITXT_COMPRESSION_NONE
1485 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1486 text_ptr[i].key - keyword for comment. Must contain
1487 1-79 characters.
1488 text_ptr[i].text - text comments for current
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]1489 keyword. Can be empty.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1490 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1491 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1492 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1493 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1494 text_ptr[i].lang - language of comment (empty
1495 string for unknown).
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1496 text_ptr[i].lang_key - keyword in UTF-8
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1497 (empty string for unknown).
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1498 num_text - number of comments (same as
1499 num_comments; you can put NULL here
1500 to avoid the duplication)
1501 Note while png_set_text() will accept text, language,
1502 and translated keywords that can be NULL pointers, the
1503 structure returned by png_get_text will always contain
1504 regular zero-terminated C strings. They might be
1505 empty strings but they will never be NULL pointers.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1506
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1507 num_spalettes = png_get_sPLT(png_ptr, info_ptr,
1508 &palette_ptr);
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1509 palette_ptr - array of palette structures holding
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1510 contents of one or more sPLT chunks
1511 read.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1512 num_spalettes - number of sPLT chunks read.
1513
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1514 png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1515 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1516 offset_x - positive offset from the left edge
1517 of the screen
1518 offset_y - positive offset from the top edge
1519 of the screen
1520 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
1521
1522 png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1523 &unit_type);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1524 res_x - pixels/unit physical resolution in
1525 x direction
1526 res_y - pixels/unit physical resolution in
1527 x direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1528 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1529 PNG_RESOLUTION_METER
1530
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1531 png_get_sCAL(png_ptr, info_ptr, &unit, &width,
1532 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1533 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1534 width - width of a pixel in physical scale units
1535 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1536 (width and height are doubles)
1537
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1538 png_get_sCAL_s(png_ptr, info_ptr, &unit, &width,
1539 &height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1540 unit - physical scale units (an integer)
1541 width - width of a pixel in physical scale units
1542 height - height of a pixel in physical scale units
1543 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1544
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1545 num_unknown_chunks = png_get_unknown_chunks(png_ptr,
1546 info_ptr, &unknowns)
1547 unknowns - array of png_unknown_chunk
1548 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1549 unknowns[i].name - name of unknown chunk
1550 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1551 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1552 unknowns[i].location - position of chunk in file
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1553
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1554 The value of "i" corresponds to the order in which the
1555 chunks were read from the PNG file or inserted with the
1556 png_set_unknown_chunks() function.
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1557
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1558The data from the pHYs chunk can be retrieved in several convenient
1559forms:
1560
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1561 res_x = png_get_x_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1562 info_ptr)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1563 res_y = png_get_y_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1564 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1565 res_x_and_y = png_get_pixels_per_meter(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1566 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1567 res_x = png_get_x_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1568 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1569 res_y = png_get_y_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1570 info_ptr)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1571 res_x_and_y = png_get_pixels_per_inch(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1572 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1573 aspect_ratio = png_get_pixel_aspect_ratio(png_ptr,
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1574 info_ptr)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1575
1576 (Each of these returns 0 [signifying "unknown"] if
1577 the data is not present or if res_x is 0;
1578 res_x_and_y is 0 if res_x != res_y)
1579
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1580The data from the oFFs chunk can be retrieved in several convenient
1581forms:
1582
1583 x_offset = png_get_x_offset_microns(png_ptr, info_ptr);
1584 y_offset = png_get_y_offset_microns(png_ptr, info_ptr);
1585 x_offset = png_get_x_offset_inches(png_ptr, info_ptr);
1586 y_offset = png_get_y_offset_inches(png_ptr, info_ptr);
1587
1588 (Each of these returns 0 [signifying "unknown" if both
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]1589 x and y are 0] if the data is not present or if the
1590 chunk is present but the unit is the pixel)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1591
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1592For more information, see the png_info definition in png.h and the
1593PNG specification for chunk contents. Be careful with trusting
1594rowbytes, as some of the transformations could increase the space
1595needed to hold a row (expand, filler, gray_to_rgb, etc.).
1596See png_read_update_info(), below.
1597
1598A quick word about text_ptr and num_text. PNG stores comments in
1599keyword/text pairs, one pair per chunk, with no limit on the number
1600of text chunks, and a 2^31 byte limit on their size. While there are
1601suggested keywords, there is no requirement to restrict the use to these
1602strings. It is strongly suggested that keywords and text be sensible
1603to humans (that's the point), so don't use abbreviations. Non-printing
1604symbols are not allowed. See the PNG specification for more details.
1605There is also no requirement to have text after the keyword.
1606
1607Keywords should be limited to 79 Latin-1 characters without leading or
1608trailing spaces, but non-consecutive spaces are allowed within the
1609keyword. It is possible to have the same keyword any number of times.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1610The text_ptr is an array of png_text structures, each holding a
1611pointer to a language string, a pointer to a keyword and a pointer to
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]1612a text string. The text string, language code, and translated
1613keyword may be empty or NULL pointers. The keyword/text
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]1614pairs are put into the array in the order that they are received.
1615However, some or all of the text chunks may be after the image, so, to
1616make sure you have read all the text chunks, don't mess with these
1617until after you read the stuff after the image. This will be
1618mentioned again below in the discussion that goes with png_read_end().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1619
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]1620.SS Input transformations
1621
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1622After you've read the header information, you can set up the library
1623to handle any special transformations of the image data. The various
1624ways to transform the data will be described in the order that they
1625should occur. This is important, as some of these change the color
1626type and/or bit depth of the data, and some others only work on
1627certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1628checks 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]1629make sure to only enable a transformation if it will be valid for the
1630data. For example, don't swap red and blue on grayscale data.
1631
1632The colors used for the background and transparency values should be
1633supplied in the same format/depth as the current image data. They
1634are stored in the same format/depth as the image data in a bKGD or tRNS
1635chunk, so this is what libpng expects for this data. The colors are
1636transformed to keep in sync with the image data when an application
1637calls the png_read_update_info() routine (see below).
1638
1639Data will be decoded into the supplied row buffers packed into bytes
1640unless the library has been told to transform it into another format.
1641For example, 4 bit/pixel paletted or grayscale data will be returned
16422 pixels/byte with the leftmost pixel in the high-order bits of the
1643byte, unless png_set_packing() is called. 8-bit RGB data will be stored
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1644in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha()
1645is called to insert filler bytes, either before or after each RGB triplet.
164616-bit RGB data will be returned RRGGBB RRGGBB, with the most significant
1647byte of the color value first, unless png_set_strip_16() is called to
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]1648transform it to regular RGB RGB triplets, or png_set_filler() or
1649png_set_add alpha() is called to insert filler bytes, either before or
1650after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can
1651be modified with
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1652png_set_filler(), png_set_add_alpha(), or png_set_strip_16().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1653
1654The following code transforms grayscale images of less than 8 to 8 bits,
1655changes paletted images to RGB, and adds a full alpha channel if there is
1656transparency information in a tRNS chunk. This is most useful on
1657grayscale images with bit depths of 2 or 4 or if there is a multiple-image
1658viewing application that wishes to treat all images in the same way.
1659
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1660 if (color_type == PNG_COLOR_TYPE_PALETTE)
1661 png_set_palette_to_rgb(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1662
1663 if (color_type == PNG_COLOR_TYPE_GRAY &&
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1664 bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1665
1666 if (png_get_valid(png_ptr, info_ptr,
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1667 PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr);
1668
1669These three functions are actually aliases for png_set_expand(), added
1670in libpng version 1.0.4, with the function names expanded to improve code
1671readability. In some future version they may actually do different
1672things.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1673
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1674As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was
1675added. It expands the sample depth without changing tRNS to alpha.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1676
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]1677As of libpng version 1.4.0beta79, not all possible expansions are supported.
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]1678
1679In the following table, the 01 means grayscale with depth<8, 31 means
1680indexed with depth<8, other numerals represent the color type, "T" means
1681the tRNS chunk is present, A means an alpha channel is present, and O
1682means tRNS or alpha is present but all pixels in the image are opaque.
1683
1684 FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O
1685 TO
1686 01 -
1687 31 -
1688 0 1 -
1689 0T -
1690 0O -
1691 2 GX -
1692 2T -
1693 2O -
1694 3 1 -
1695 3T -
1696 3O -
1697 4A T -
1698 4O -
1699 6A GX TX TX -
1700 6O GX TX -
1701
1702Within the matrix,
1703 "-" means the transformation is not supported.
1704 "X" means the transformation is obtained by png_set_expand().
1705 "1" means the transformation is obtained by
1706 png_set_expand_gray_1_2_4_to_8
1707 "G" means the transformation is obtained by
1708 png_set_gray_to_rgb().
1709 "P" means the transformation is obtained by
1710 png_set_expand_palette_to_rgb().
1711 "T" means the transformation is obtained by
1712 png_set_tRNS_to_alpha().
Glenn Randers-Pehrson1ce08362006-03-08 23:35:59 -0600[diff] [blame]1713
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1714PNG can have files with 16 bits per channel. If you only can handle
17158 bits per channel, this will strip the pixels down to 8 bit.
1716
1717 if (bit_depth == 16)
1718 png_set_strip_16(png_ptr);
1719
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1720If, for some reason, you don't need the alpha channel on an image,
1721and you want to remove it rather than combining it with the background
1722(but the image author certainly had in mind that you *would* combine
1723it with the background, so that's what you should probably do):
1724
1725 if (color_type & PNG_COLOR_MASK_ALPHA)
1726 png_set_strip_alpha(png_ptr);
1727
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1728In PNG files, the alpha channel in an image
1729is the level of opacity. If you need the alpha channel in an image to
1730be the level of transparency instead of opacity, you can invert the
1731alpha channel (or the tRNS chunk data) after it's read, so that 0 is
1732fully opaque and 255 (in 8-bit or paletted images) or 65535 (in 16-bit
1733images) is fully transparent, with
1734
1735 png_set_invert_alpha(png_ptr);
1736
Glenn Randers-Pehrson1916f6a2008-08-14 13:44:49 -0500[diff] [blame]1737The PNG format only supports pixels with postmultiplied alpha.
1738If you want to replace the pixels, after reading them, with pixels
1739that have premultiplied color samples, you can do this with
1740
1741 png_set_premultiply_alpha(png_ptr);
1742
Glenn Randers-Pehrson41983602008-08-18 21:52:21 -0500[diff] [blame]1743If you do this, any input with a tRNS chunk will be expanded to
1744have an alpha channel.
1745
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1746PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
1747they can, resulting in, for example, 8 pixels per byte for 1 bit
1748files. This code expands to 1 pixel per byte without changing the
1749values of the pixels:
1750
1751 if (bit_depth < 8)
1752 png_set_packing(png_ptr);
1753
1754PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels
1755stored in a PNG image have been "scaled" or "shifted" up to the next
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1756higher possible bit depth (e.g. from 5 bits/sample in the range [0,31] to
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]17578 bits/sample in the range [0, 255]). However, it is also possible to
1758convert the PNG pixel data back to the original bit depth of the image.
1759This call reduces the pixels back down to the original bit depth:
1760
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]1761 png_color_8p sig_bit;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1762
1763 if (png_get_sBIT(png_ptr, info_ptr, &sig_bit))
1764 png_set_shift(png_ptr, sig_bit);
1765
1766PNG files store 3-color pixels in red, green, blue order. This code
1767changes the storage of the pixels to blue, green, red:
1768
1769 if (color_type == PNG_COLOR_TYPE_RGB ||
1770 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1771 png_set_bgr(png_ptr);
1772
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1773PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them
1774into 4 or 8 bytes for windowing systems that need them in this format:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1775
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1776 if (color_type == PNG_COLOR_TYPE_RGB)
1777 png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1778
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]1779where "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]1780either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether
1781you want the filler before the RGB or after. This transformation
Glenn Randers-Pehrson1b8e5672001-08-25 06:46:06 -0500[diff] [blame]1782does not affect images that already have full alpha channels. To add an
1783opaque alpha channel, use filler=0xff or 0xffff and PNG_FILLER_AFTER which
1784will generate RGBA pixels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1785
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1786Note that png_set_filler() does not change the color type. If you want
1787to do that, you can add a true alpha channel with
1788
1789 if (color_type == PNG_COLOR_TYPE_RGB ||
1790 color_type == PNG_COLOR_TYPE_GRAY)
1791 png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER);
1792
1793where "filler" contains the alpha value to assign to each pixel.
Glenn Randers-Pehrson16e11662004-11-01 14:13:40 -0600[diff] [blame]1794This function was added in libpng-1.2.7.
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]1795
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1796If you are reading an image with an alpha channel, and you need the
1797data as ARGB instead of the normal PNG format RGBA:
1798
1799 if (color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1800 png_set_swap_alpha(png_ptr);
1801
1802For some uses, you may want a grayscale image to be represented as
1803RGB. This code will do that conversion:
1804
1805 if (color_type == PNG_COLOR_TYPE_GRAY ||
1806 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
1807 png_set_gray_to_rgb(png_ptr);
1808
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1809Conversely, you can convert an RGB or RGBA image to grayscale or grayscale
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1810with alpha.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1811
1812 if (color_type == PNG_COLOR_TYPE_RGB ||
1813 color_type == PNG_COLOR_TYPE_RGB_ALPHA)
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1814 png_set_rgb_to_gray_fixed(png_ptr, error_action,
1815 int red_weight, int green_weight);
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1816
1817 error_action = 1: silently do the conversion
1818 error_action = 2: issue a warning if the original
1819 image has any pixel where
1820 red != green or red != blue
1821 error_action = 3: issue an error and abort the
1822 conversion if the original
1823 image has any pixel where
1824 red != green or red != blue
1825
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1826 red_weight: weight of red component times 100000
1827 green_weight: weight of green component times 100000
1828 If either weight is negative, default
1829 weights (21268, 71514) are used.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1830
1831If you have set error_action = 1 or 2, you can
1832later check whether the image really was gray, after processing
1833the image rows, with the png_get_rgb_to_gray_status(png_ptr) function.
1834It will return a png_byte that is zero if the image was gray or
18351 if there were any non-gray pixels. bKGD and sBIT data
1836will be silently converted to grayscale, using the green channel
1837data, regardless of the error_action setting.
1838
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1839With red_weight+green_weight<=100000,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1840the normalized graylevel is computed:
1841
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1842 int rw = red_weight * 65536;
1843 int gw = green_weight * 65536;
1844 int bw = 65536 - (rw + gw);
1845 gray = (rw*red + gw*green + bw*blue)/65536;
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1846
1847The default values approximate those recommended in the Charles
1848Poynton's Color FAQ, <http://www.inforamp.net/~poynton/>
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]1849Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net>
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1850
1851 Y = 0.212671 * R + 0.715160 * G + 0.072169 * B
1852
1853Libpng approximates this with
1854
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1855 Y = 0.21268 * R + 0.7151 * G + 0.07217 * B
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1856
1857which can be expressed with integers as
1858
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1859 Y = (6969 * R + 23434 * G + 2365 * B)/32768
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1860
1861The calculation is done in a linear colorspace, if the image gamma
1862is known.
1863
Glenn Randers-Pehrson73d57cb2002-03-25 18:49:08 -0600[diff] [blame]1864If you have a grayscale and you are using png_set_expand_depth(),
1865png_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]1866a higher bit-depth, you must either supply the background color as a gray
1867value at the original file bit-depth (need_expand = 1) or else supply the
1868background color as an RGB triplet at the final, expanded bit depth
1869(need_expand = 0). Similarly, if you are reading a paletted image, you
1870must either supply the background color as a palette index (need_expand = 1)
1871or 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]1872
1873 png_color_16 my_background;
1874 png_color_16p image_background;
1875
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]1876 if (png_get_bKGD(png_ptr, info_ptr, &image_background))
1877 png_set_background(png_ptr, image_background,
1878 PNG_BACKGROUND_GAMMA_FILE, 1, 1.0);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1879 else
1880 png_set_background(png_ptr, &my_background,
1881 PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0);
1882
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]1883The png_set_background() function tells libpng to composite images
1884with alpha or simple transparency against the supplied background
1885color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid),
1886you may use this color, or supply another color more suitable for
1887the current display (e.g., the background color from a web page). You
1888need to tell libpng whether the color is in the gamma space of the
1889display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file
1890(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one
1891that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't
1892know why anyone would use this, but it's here).
1893
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1894To properly display PNG images on any kind of system, the application needs
1895to know what the display gamma is. Ideally, the user will know this, and
1896the application will allow them to set it. One method of allowing the user
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1897to set the display gamma separately for each system is to check for a
1898SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be
1899correctly set.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1900
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]1901Note that display_gamma is the overall gamma correction required to produce
1902pleasing results, which depends on the lighting conditions in the surrounding
1903environment. In a dim or brightly lit room, no compensation other than
1904the physical gamma exponent of the monitor is needed, while in a dark room
1905a slightly smaller exponent is better.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1906
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1907 double gamma, screen_gamma;
1908
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1909 if (/* We have a user-defined screen
1910 gamma value */)
1911 {
1912 screen_gamma = user_defined_screen_gamma;
1913 }
1914 /* One way that applications can share the same
1915 screen gamma value */
1916 else if ((gamma_str = getenv("SCREEN_GAMMA"))
1917 != NULL)
1918 {
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]1919 screen_gamma = (double)atof(gamma_str);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1920 }
1921 /* If we don't have another value */
1922 else
1923 {
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1924 screen_gamma = 2.2; /* A good guess for a
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1925 PC monitor in a bright office or a dim room */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1926 screen_gamma = 2.0; /* A good guess for a
1927 PC monitor in a dark room */
1928 screen_gamma = 1.7 or 1.0; /* A good
1929 guess for Mac systems */
1930 }
1931
1932The png_set_gamma() function handles gamma transformations of the data.
1933Pass both the file gamma and the current screen_gamma. If the file does
1934not 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]1935it 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]1936that file gammas are inverted from screen gammas. See the discussions
1937on gamma in the PNG specification for an excellent description of what
1938gamma is, and why all applications should support it. It is strongly
1939recommended that PNG viewers support gamma correction.
1940
1941 if (png_get_gAMA(png_ptr, info_ptr, &gamma))
1942 png_set_gamma(png_ptr, screen_gamma, gamma);
1943 else
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]1944 png_set_gamma(png_ptr, screen_gamma, 0.45455);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1945
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1946PNG files describe monochrome as black being zero and white being one.
1947The following code will reverse this (make black be one and white be
1948zero):
1949
Glenn Randers-Pehrson1ea0ff32001-08-07 22:25:59 -0500[diff] [blame]1950 if (bit_depth == 1 && color_type == PNG_COLOR_TYPE_GRAY)
1951 png_set_invert_mono(png_ptr);
1952
1953This function can also be used to invert grayscale and gray-alpha images:
1954
1955 if (color_type == PNG_COLOR_TYPE_GRAY ||
1956 color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1957 png_set_invert_mono(png_ptr);
1958
1959PNG files store 16 bit pixels in network byte order (big-endian,
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]1960ie. most significant bits first). This code changes the storage to the
1961other way (little-endian, i.e. least significant bits first, the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]1962way PCs store them):
1963
1964 if (bit_depth == 16)
1965 png_set_swap(png_ptr);
1966
1967If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
1968need to change the order the pixels are packed into bytes, you can use:
1969
1970 if (bit_depth < 8)
1971 png_set_packswap(png_ptr);
1972
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]1973Finally, you can write your own transformation function if none of
1974the existing ones meets your needs. This is done by setting a callback
1975with
1976
1977 png_set_read_user_transform_fn(png_ptr,
1978 read_transform_fn);
1979
1980You must supply the function
1981
1982 void read_transform_fn(png_ptr ptr, row_info_ptr
1983 row_info, png_bytep data)
1984
1985See pngtest.c for a working example. Your function will be called
1986after all of the other transformations have been processed.
1987
1988You can also set up a pointer to a user structure for use by your
1989callback function, and you can inform libpng that your transform
1990function will change the number of channels or bit depth with the
1991function
1992
1993 png_set_user_transform_info(png_ptr, user_ptr,
1994 user_depth, user_channels);
1995
1996The user's application, not libpng, is responsible for allocating and
1997freeing any memory required for the user structure.
1998
1999You can retrieve the pointer via the function
2000png_get_user_transform_ptr(). For example:
2001
2002 voidp read_user_transform_ptr =
2003 png_get_user_transform_ptr(png_ptr);
2004
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2005The last thing to handle is interlacing; this is covered in detail below,
2006but you must call the function here if you want libpng to handle expansion
2007of the interlaced image.
2008
2009 number_of_passes = png_set_interlace_handling(png_ptr);
2010
2011After setting the transformations, libpng can update your png_info
2012structure to reflect any transformations you've requested with this
2013call. This is most useful to update the info structure's rowbytes
2014field so you can use it to allocate your image memory. This function
2015will also update your palette with the correct screen_gamma and
2016background if these have been given with the calls above.
2017
2018 png_read_update_info(png_ptr, info_ptr);
2019
2020After you call png_read_update_info(), you can allocate any
2021memory you need to hold the image. The row data is simply
2022raw byte data for all forms of images. As the actual allocation
2023varies among applications, no example will be given. If you
2024are allocating one large chunk, you will need to build an
2025array of pointers to each row, as it will be needed for some
2026of the functions below.
2027
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2028.SS Reading image data
2029
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2030After you've allocated memory, you can read the image data.
2031The simplest way to do this is in one function call. If you are
2032allocating enough memory to hold the whole image, you can just
2033call png_read_image() and libpng will read in all the image data
2034and put it in the memory area supplied. You will need to pass in
2035an array of pointers to each row.
2036
2037This function automatically handles interlacing, so you don't need
2038to call png_set_interlace_handling() or call this function multiple
2039times, or any of that other stuff necessary with png_read_rows().
2040
2041 png_read_image(png_ptr, row_pointers);
2042
2043where row_pointers is:
2044
2045 png_bytep row_pointers[height];
2046
2047You can point to void or char or whatever you use for pixels.
2048
2049If you don't want to read in the whole image at once, you can
2050use png_read_rows() instead. If there is no interlacing (check
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2051interlace_type == PNG_INTERLACE_NONE), this is simple:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2052
2053 png_read_rows(png_ptr, row_pointers, NULL,
2054 number_of_rows);
2055
2056where row_pointers is the same as in the png_read_image() call.
2057
2058If 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]2059a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2060
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2061 png_bytep row_pointer = row;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2062 png_read_row(png_ptr, row_pointer, NULL);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2063
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2064If the file is interlaced (interlace_type != 0 in the IHDR chunk), things
2065get somewhat harder. The only current (PNG Specification version 1.2)
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2066interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2067is a somewhat complicated 2D interlace scheme, known as Adam7, that
2068breaks down an image into seven smaller images of varying size, based
2069on an 8x8 grid.
2070
2071libpng can fill out those images or it can give them to you "as is".
2072If you want them filled out, there are two ways to do that. The one
2073mentioned in the PNG specification is to expand each pixel to cover
2074those pixels that have not been read yet (the "rectangle" method).
2075This results in a blocky image for the first pass, which gradually
2076smooths out as more pixels are read. The other method is the "sparkle"
2077method, where pixels are drawn only in their final locations, with the
2078rest of the image remaining whatever colors they were initialized to
2079before the start of the read. The first method usually looks better,
2080but tends to be slower, as there are more pixels to put in the rows.
2081
2082If you don't want libpng to handle the interlacing details, just call
2083png_read_rows() seven times to read in all seven images. Each of the
2084images is a valid image by itself, or they can all be combined on an
20858x8 grid to form a single image (although if you intend to combine them
2086you would be far better off using the libpng interlace handling).
2087
2088The first pass will return an image 1/8 as wide as the entire image
2089(every 8th column starting in column 0) and 1/8 as high as the original
2090(every 8th row starting in row 0), the second will be 1/8 as wide
2091(starting in column 4) and 1/8 as high (also starting in row 0). The
2092third pass will be 1/4 as wide (every 4th pixel starting in column 0) and
20931/8 as high (every 8th row starting in row 4), and the fourth pass will
2094be 1/4 as wide and 1/4 as high (every 4th column starting in column 2,
2095and every 4th row starting in row 0). The fifth pass will return an
2096image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2),
2097while the sixth pass will be 1/2 as wide and 1/2 as high as the original
2098(starting in column 1 and row 0). The seventh and final pass will be as
2099wide as the original, and 1/2 as high, containing all of the odd
2100numbered scanlines. Phew!
2101
2102If you want libpng to expand the images, call this before calling
2103png_start_read_image() or png_read_update_info():
2104
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2105 if (interlace_type == PNG_INTERLACE_ADAM7)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2106 number_of_passes
2107 = png_set_interlace_handling(png_ptr);
2108
2109This will return the number of passes needed. Currently, this
2110is seven, but may change if another interlace type is added.
2111This function can be called even if the file is not interlaced,
2112where it will return one pass.
2113
2114If you are not going to display the image after each pass, but are
2115going to wait until the entire image is read in, use the sparkle
2116effect. This effect is faster and the end result of either method
2117is exactly the same. If you are planning on displaying the image
2118after each pass, the "rectangle" effect is generally considered the
2119better looking one.
2120
2121If you only want the "sparkle" effect, just call png_read_rows() as
2122normal, with the third parameter NULL. Make sure you make pass over
2123the image number_of_passes times, and you don't change the data in the
2124rows between calls. You can change the locations of the data, just
2125not the data. Each pass only writes the pixels appropriate for that
2126pass, and assumes the data from previous passes is still valid.
2127
2128 png_read_rows(png_ptr, row_pointers, NULL,
2129 number_of_rows);
2130
2131If you only want the first effect (the rectangles), do the same as
2132before except pass the row buffer in the third parameter, and leave
2133the second parameter NULL.
2134
2135 png_read_rows(png_ptr, NULL, row_pointers,
2136 number_of_rows);
2137
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2138.SS Finishing a sequential read
2139
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]2140After you are finished reading the image through the
2141low-level interface, you can finish reading the file. If you are
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2142interested in comments or time, which may be stored either before or
2143after the image data, you should pass the separate png_info struct if
2144you want to keep the comments from before and after the image
2145separate. If you are not interested, you can pass NULL.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2146
2147 png_read_end(png_ptr, end_info);
2148
2149When you are done, you can free all memory allocated by libpng like this:
2150
2151 png_destroy_read_struct(&png_ptr, &info_ptr,
2152 &end_info);
2153
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2154It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2155point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2156
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2157 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2158 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2159 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2160 more of
2161 PNG_FREE_PLTE, PNG_FREE_TRNS,
2162 PNG_FREE_HIST, PNG_FREE_ICCP,
2163 PNG_FREE_PCAL, PNG_FREE_ROWS,
2164 PNG_FREE_SCAL, PNG_FREE_SPLT,
2165 PNG_FREE_TEXT, PNG_FREE_UNKN,
2166 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2167 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2168 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2169
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2170This function may be safely called when the relevant storage has
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2171already been freed, or has not yet been allocated, or was allocated
2172by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2173cases do nothing. The "seq" parameter is ignored if only one item
2174of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2175-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2176the mask, such as text or sPLT, only the n'th item in the structure
2177is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2178
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2179The default behavior is only to free data that was allocated internally
2180by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2181or so that it will free data that was allocated by the user with png_malloc()
2182or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2183
2184 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2185 mask - which data elements are affected
2186 same choices as in png_free_data()
2187 freer - one of
2188 PNG_DESTROY_WILL_FREE_DATA
2189 PNG_SET_WILL_FREE_DATA
2190 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2191
2192This function only affects data that has already been allocated.
2193You can call this function after reading the PNG data but before calling
2194any png_set_*() functions, to control whether the user or the png_set_*()
2195function is responsible for freeing any existing data that might be present,
2196and again after the png_set_*() functions to control whether the user
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2197or png_destroy_*() is supposed to free the data. When the user assumes
2198responsibility for libpng-allocated data, the application must use
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2199png_free() to free it, and when the user transfers responsibility to libpng
2200for data that the user has allocated, the user must have used png_malloc()
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]2201or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2202
2203If you allocated your row_pointers in a single block, as suggested above in
2204the description of the high level read interface, you must not transfer
2205responsibility for freeing it to the png_set_rows or png_read_destroy function,
2206because they would also try to free the individual row_pointers[i].
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2207
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2208If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
2209separately, do not transfer responsibility for freeing text_ptr to libpng,
2210because when libpng fills a png_text structure it combines these members with
2211the key member, and png_free_data() will free only text_ptr.key. Similarly,
2212if you transfer responsibility for free'ing text_ptr from libpng to your
2213application, your application must not separately free those members.
2214
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2215The png_free_data() function will turn off the "valid" flag for anything
2216it frees. If you need to turn the flag off for a chunk that was freed by your
2217application instead of by libpng, you can use
2218
2219 png_set_invalid(png_ptr, info_ptr, mask);
2220 mask - identifies the chunks to be made invalid,
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2221 containing the bitwise OR of one or
Glenn Randers-Pehrsond56aca72000-11-23 11:51:42 -0600[diff] [blame]2222 more of
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]2223 PNG_INFO_gAMA, PNG_INFO_sBIT,
2224 PNG_INFO_cHRM, PNG_INFO_PLTE,
2225 PNG_INFO_tRNS, PNG_INFO_bKGD,
2226 PNG_INFO_hIST, PNG_INFO_pHYs,
2227 PNG_INFO_oFFs, PNG_INFO_tIME,
2228 PNG_INFO_pCAL, PNG_INFO_sRGB,
2229 PNG_INFO_iCCP, PNG_INFO_sPLT,
2230 PNG_INFO_sCAL, PNG_INFO_IDAT
2231
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2232For a more compact example of reading a PNG image, see the file example.c.
2233
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2234.SS Reading PNG files progressively
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2235
2236The progressive reader is slightly different then the non-progressive
2237reader. Instead of calling png_read_info(), png_read_rows(), and
2238png_read_end(), you make one call to png_process_data(), which calls
2239callbacks when it has the info, a row, or the end of the image. You
2240set up these callbacks with png_set_progressive_read_fn(). You don't
2241have to worry about the input/output functions of libpng, as you are
2242giving the library the data directly in png_process_data(). I will
2243assume that you have read the section on reading PNG files above,
2244so I will only highlight the differences (although I will show
2245all of the code).
2246
2247png_structp png_ptr;
2248png_infop info_ptr;
2249
2250 /* An example code fragment of how you would
2251 initialize the progressive reader in your
2252 application. */
2253 int
2254 initialize_png_reader()
2255 {
2256 png_ptr = png_create_read_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2257 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2258 user_error_fn, user_warning_fn);
2259 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2260 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2261 info_ptr = png_create_info_struct(png_ptr);
2262 if (!info_ptr)
2263 {
2264 png_destroy_read_struct(&png_ptr, (png_infopp)NULL,
2265 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2266 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2267 }
2268
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2269 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2270 {
2271 png_destroy_read_struct(&png_ptr, &info_ptr,
2272 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2273 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2274 }
2275
2276 /* This one's new. You can provide functions
2277 to be called when the header info is valid,
2278 when each row is completed, and when the image
2279 is finished. If you aren't using all functions,
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2280 you can specify NULL parameters. Even when all
2281 three functions are NULL, you need to call
2282 png_set_progressive_read_fn(). You can use
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2283 any struct as the user_ptr (cast to a void pointer
2284 for the function call), and retrieve the pointer
2285 from inside the callbacks using the function
2286
2287 png_get_progressive_ptr(png_ptr);
2288
2289 which will return a void pointer, which you have
2290 to cast appropriately.
2291 */
2292 png_set_progressive_read_fn(png_ptr, (void *)user_ptr,
2293 info_callback, row_callback, end_callback);
2294
2295 return 0;
2296 }
2297
2298 /* A code fragment that you call as you receive blocks
2299 of data */
2300 int
2301 process_data(png_bytep buffer, png_uint_32 length)
2302 {
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2303 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2304 {
2305 png_destroy_read_struct(&png_ptr, &info_ptr,
2306 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2307 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2308 }
2309
2310 /* This one's new also. Simply give it a chunk
2311 of data from the file stream (in order, of
2312 course). On machines with segmented memory
2313 models machines, don't give it any more than
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2314 64K. The library seems to run fine with sizes
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2315 of 4K. Although you can give it much less if
2316 necessary (I assume you can give it chunks of
2317 1 byte, I haven't tried less then 256 bytes
2318 yet). When this function returns, you may
2319 want to display any rows that were generated
2320 in the row callback if you don't already do
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2321 so there.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2322 */
2323 png_process_data(png_ptr, info_ptr, buffer, length);
2324 return 0;
2325 }
2326
2327 /* This function is called (as set by
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2328 png_set_progressive_read_fn() above) when enough data
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2329 has been supplied so all of the header has been
2330 read.
2331 */
2332 void
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2333 info_callback(png_structp png_ptr, png_infop info)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2334 {
2335 /* Do any setup here, including setting any of
2336 the transformations mentioned in the Reading
2337 PNG files section. For now, you _must_ call
2338 either png_start_read_image() or
2339 png_read_update_info() after all the
2340 transformations are set (even if you don't set
2341 any). You may start getting rows before
2342 png_process_data() returns, so this is your
2343 last chance to prepare for that.
2344 */
2345 }
2346
2347 /* This function is called when each row of image
2348 data is complete */
2349 void
2350 row_callback(png_structp png_ptr, png_bytep new_row,
Glenn Randers-Pehrsone68f5a32001-05-14 09:20:53 -0500[diff] [blame]2351 png_uint_32 row_num, int pass)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2352 {
2353 /* If the image is interlaced, and you turned
2354 on the interlace handler, this function will
2355 be called for every row in every pass. Some
2356 of these rows will not be changed from the
2357 previous pass. When the row is not changed,
2358 the new_row variable will be NULL. The rows
2359 and passes are called in order, so you don't
2360 really need the row_num and pass, but I'm
2361 supplying them because it may make your life
2362 easier.
2363
2364 For the non-NULL rows of interlaced images,
2365 you must call png_progressive_combine_row()
2366 passing in the row and the old row. You can
2367 call this function for NULL rows (it will just
2368 return) and for non-interlaced images (it just
2369 does the memcpy for you) if it will make the
2370 code easier. Thus, you can just do this for
2371 all cases:
2372 */
2373
2374 png_progressive_combine_row(png_ptr, old_row,
2375 new_row);
2376
2377 /* where old_row is what was displayed for
Glenn Randers-Pehrson345bc271998-06-14 14:43:31 -0500[diff] [blame]2378 previously for the row. Note that the first
2379 pass (pass == 0, really) will completely cover
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2380 the old row, so the rows do not have to be
2381 initialized. After the first pass (and only
2382 for interlaced images), you will have to pass
2383 the current row, and the function will combine
2384 the old row and the new row.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2385 */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2386 }
2387
2388 void
2389 end_callback(png_structp png_ptr, png_infop info)
2390 {
2391 /* This function is called after the whole image
2392 has been read, including any chunks after the
2393 image (up to and including the IEND). You
2394 will usually have the same info chunk as you
2395 had in the header, although some data may have
2396 been added to the comments and time fields.
2397
2398 Most people won't do much here, perhaps setting
2399 a flag that marks the image as finished.
2400 */
2401 }
2402
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2403
2404
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2405.SH IV. Writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2406
2407Much of this is very similar to reading. However, everything of
2408importance is repeated here, so you won't have to constantly look
2409back up in the reading section to understand writing.
2410
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2411.SS Setup
2412
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2413You will want to do the I/O initialization before you get into libpng,
2414so if it doesn't work, you don't have anything to undo. If you are not
2415using the standard I/O functions, you will need to replace them with
2416custom writing functions. See the discussion under Customizing libpng.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2417
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2418 FILE *fp = fopen(file_name, "wb");
2419 if (!fp)
2420 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2421 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2422 }
2423
2424Next, png_struct and png_info need to be allocated and initialized.
2425As these can be both relatively large, you may not want to store these
2426on the stack, unless you have stack space to spare. Of course, you
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2427will want to check if they return NULL. If you are also reading,
2428you won't want to name your read structure and your write structure
2429both "png_ptr"; you can call them anything you like, such as
2430"read_ptr" and "write_ptr". Look at pngtest.c, for example.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2431
2432 png_structp png_ptr = png_create_write_struct
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]2433 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2434 user_error_fn, user_warning_fn);
2435 if (!png_ptr)
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2436 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2437
2438 png_infop info_ptr = png_create_info_struct(png_ptr);
2439 if (!info_ptr)
2440 {
2441 png_destroy_write_struct(&png_ptr,
2442 (png_infopp)NULL);
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2443 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2444 }
2445
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2446If you want to use your own memory allocation routines,
2447define PNG_USER_MEM_SUPPORTED and use
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2448png_create_write_struct_2() instead of png_create_write_struct():
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]2449
2450 png_structp png_ptr = png_create_write_struct_2
2451 (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr,
2452 user_error_fn, user_warning_fn, (png_voidp)
2453 user_mem_ptr, user_malloc_fn, user_free_fn);
2454
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2455After you have these structures, you will need to set up the
2456error handling. When libpng encounters an error, it expects to
2457longjmp() back to your routine. Therefore, you will need to call
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2458setjmp() and pass the png_jmpbuf(png_ptr). If you
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2459write the file from different routines, you will need to update
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2460the png_jmpbuf(png_ptr) every time you enter a new routine that will
2461call a png_*() function. See your documentation of setjmp/longjmp
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2462for your compiler for more information on setjmp/longjmp. See
2463the discussion on libpng error handling in the Customizing Libpng
2464section below for more information on the libpng error handling.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2465
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2466 if (setjmp(png_jmpbuf(png_ptr)))
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2467 {
Glenn Randers-Pehrson104622b2000-05-29 08:58:03 -0500[diff] [blame]2468 png_destroy_write_struct(&png_ptr, &info_ptr);
2469 fclose(fp);
2470 return (ERROR);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2471 }
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2472 ...
2473 return;
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2474
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2475If you would rather avoid the complexity of setjmp/longjmp issues,
2476you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case
2477errors will result in a call to PNG_ABORT() which defaults to abort().
2478
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2479Now you need to set up the output code. The default for libpng is to
2480use the C function fwrite(). If you use this, you will need to pass a
2481valid FILE * in the function png_init_io(). Be sure that the file is
2482opened in binary mode. Again, if you wish to handle writing data in
2483another way, see the discussion on libpng I/O handling in the Customizing
2484Libpng section below.
2485
2486 png_init_io(png_ptr, fp);
2487
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]2488If you are embedding your PNG into a datastream such as MNG, and don't
2489want libpng to write the 8-byte signature, or if you have already
2490written the signature in your application, use
2491
2492 png_set_sig_bytes(png_ptr, 8);
2493
2494to inform libpng that it should not write a signature.
2495
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2496.SS Write callbacks
2497
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2498At this point, you can set up a callback function that will be
2499called after each row has been written, which you can use to control
2500a progress meter or the like. It's demonstrated in pngtest.c.
2501You must supply a function
2502
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2503 void write_row_callback(png_ptr, png_uint_32 row,
2504 int pass);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]2505 {
2506 /* put your code here */
2507 }
2508
2509(You can give it another name that you like instead of "write_row_callback")
2510
2511To inform libpng about your function, use
2512
2513 png_set_write_status_fn(png_ptr, write_row_callback);
2514
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2515You now have the option of modifying how the compression library will
2516run. The following functions are mainly for testing, but may be useful
2517in some cases, like if you need to write PNG files extremely fast and
2518are willing to give up some compression, or if you want to get the
2519maximum possible compression at the expense of slower writing. If you
2520have no special needs in this area, let the library do what it wants by
2521not calling this function at all, as it has been tuned to deliver a good
2522speed/compression ratio. The second parameter to png_set_filter() is
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2523the filter method, for which the only valid values are 0 (as of the
2524July 1999 PNG specification, version 1.2) or 64 (if you are writing
2525a PNG datastream that is to be embedded in a MNG datastream). The third
2526parameter is a flag that indicates which filter type(s) are to be tested
2527for each scanline. See the PNG specification for details on the specific filter
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2528types.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2529
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2530
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2531 /* turn on or off filtering, and/or choose
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2532 specific filters. You can use either a single
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2533 PNG_FILTER_VALUE_NAME or the bitwise OR of one
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2534 or more PNG_FILTER_NAME masks. */
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2535 png_set_filter(png_ptr, 0,
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2536 PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE |
2537 PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB |
2538 PNG_FILTER_UP | PNG_FILTER_VALUE_UP |
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]2539 PNG_FILTER_AVG | PNG_FILTER_VALUE_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2540 PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH|
2541 PNG_ALL_FILTERS);
2542
2543If an application
2544wants to start and stop using particular filters during compression,
2545it should start out with all of the filters (to ensure that the previous
2546row of pixels will be stored in case it's needed later), and then add
2547and remove them after the start of compression.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2548
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2549If you are writing a PNG datastream that is to be embedded in a MNG
2550datastream, the second parameter can be either 0 or 64.
2551
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2552The png_set_compression_*() functions interface to the zlib compression
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2553library, and should mostly be ignored unless you really know what you are
2554doing. The only generally useful call is png_set_compression_level()
2555which changes how much time zlib spends on trying to compress the image
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2556data. See the Compression Library (zlib.h and algorithm.txt, distributed
2557with zlib) for details on the compression levels.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2558
2559 /* set the zlib compression level */
2560 png_set_compression_level(png_ptr,
2561 Z_BEST_COMPRESSION);
2562
2563 /* set other zlib parameters */
2564 png_set_compression_mem_level(png_ptr, 8);
2565 png_set_compression_strategy(png_ptr,
2566 Z_DEFAULT_STRATEGY);
2567 png_set_compression_window_bits(png_ptr, 15);
2568 png_set_compression_method(png_ptr, 8);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2569 png_set_compression_buffer_size(png_ptr, 8192)
2570
2571extern PNG_EXPORT(void,png_set_zbuf_size)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2572
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2573.SS Setting the contents of info for output
2574
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2575You now need to fill in the png_info structure with all the data you
2576wish to write before the actual image. Note that the only thing you
2577are allowed to write after the image is the text chunks and the time
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]2578chunk (as of PNG Specification 1.2, anyway). See png_write_end() and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2579the latest PNG specification for more information on that. If you
2580wish to write them before the image, fill them in now, and flag that
2581data as being valid. If you want to wait until after the data, don't
2582fill them until png_write_end(). For all the fields in png_info and
2583their data types, see png.h. For explanations of what the fields
2584contain, see the PNG specification.
2585
2586Some of the more important parts of the png_info are:
2587
2588 png_set_IHDR(png_ptr, info_ptr, width, height,
2589 bit_depth, color_type, interlace_type,
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2590 compression_type, filter_method)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2591 width - holds the width of the image
2592 in pixels (up to 2^31).
2593 height - holds the height of the image
2594 in pixels (up to 2^31).
2595 bit_depth - holds the bit depth of one of the
2596 image channels.
2597 (valid values are 1, 2, 4, 8, 16
2598 and depend also on the
2599 color_type. See also significant
2600 bits (sBIT) below).
2601 color_type - describes which color/alpha
2602 channels are present.
2603 PNG_COLOR_TYPE_GRAY
2604 (bit depths 1, 2, 4, 8, 16)
2605 PNG_COLOR_TYPE_GRAY_ALPHA
2606 (bit depths 8, 16)
2607 PNG_COLOR_TYPE_PALETTE
2608 (bit depths 1, 2, 4, 8)
2609 PNG_COLOR_TYPE_RGB
2610 (bit_depths 8, 16)
2611 PNG_COLOR_TYPE_RGB_ALPHA
2612 (bit_depths 8, 16)
2613
2614 PNG_COLOR_MASK_PALETTE
2615 PNG_COLOR_MASK_COLOR
2616 PNG_COLOR_MASK_ALPHA
2617
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2618 interlace_type - PNG_INTERLACE_NONE or
2619 PNG_INTERLACE_ADAM7
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2620 compression_type - (must be
2621 PNG_COMPRESSION_TYPE_DEFAULT)
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]2622 filter_method - (must be PNG_FILTER_TYPE_DEFAULT
2623 or, if you are writing a PNG to
2624 be embedded in a MNG datastream,
2625 can also be
2626 PNG_INTRAPIXEL_DIFFERENCING)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2627
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2628If you call png_set_IHDR(), the call must appear before any of the
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]2629other png_set_*() functions, because they might require access to some of
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]2630the IHDR settings. The remaining png_set_*() functions can be called
2631in any order.
2632
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]2633If you wish, you can reset the compression_type, interlace_type, or
2634filter_method later by calling png_set_IHDR() again; if you do this, the
2635width, height, bit_depth, and color_type must be the same in each call.
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]2636
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2637 png_set_PLTE(png_ptr, info_ptr, palette,
2638 num_palette);
2639 palette - the palette for the file
2640 (array of png_color)
2641 num_palette - number of entries in the palette
2642
2643 png_set_gAMA(png_ptr, info_ptr, gamma);
2644 gamma - the gamma the image was created
2645 at (PNG_INFO_gAMA)
2646
2647 png_set_sRGB(png_ptr, info_ptr, srgb_intent);
2648 srgb_intent - the rendering intent
2649 (PNG_INFO_sRGB) The presence of
2650 the sRGB chunk means that the pixel
2651 data is in the sRGB color space.
2652 This chunk also implies specific
2653 values of gAMA and cHRM. Rendering
2654 intent is the CSS-1 property that
2655 has been defined by the International
2656 Color Consortium
2657 (http://www.color.org).
2658 It can be one of
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2659 PNG_sRGB_INTENT_SATURATION,
2660 PNG_sRGB_INTENT_PERCEPTUAL,
2661 PNG_sRGB_INTENT_ABSOLUTE, or
2662 PNG_sRGB_INTENT_RELATIVE.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2663
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2664
2665 png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr,
2666 srgb_intent);
2667 srgb_intent - the rendering intent
2668 (PNG_INFO_sRGB) The presence of the
2669 sRGB chunk means that the pixel
2670 data is in the sRGB color space.
2671 This function also causes gAMA and
2672 cHRM chunks with the specific values
2673 that are consistent with sRGB to be
2674 written.
2675
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2676 png_set_iCCP(png_ptr, info_ptr, name, compression_type,
2677 profile, proflen);
2678 name - The profile name.
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2679 compression - The compression type; always
2680 PNG_COMPRESSION_TYPE_BASE for PNG 1.0.
2681 You may give NULL to this argument to
2682 ignore it.
2683 profile - International Color Consortium color
2684 profile data. May contain NULs.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2685 proflen - length of profile data in bytes.
2686
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2687 png_set_sBIT(png_ptr, info_ptr, sig_bit);
2688 sig_bit - the number of significant bits for
2689 (PNG_INFO_sBIT) each of the gray, red,
2690 green, and blue channels, whichever are
2691 appropriate for the given color type
2692 (png_color_16)
2693
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]2694 png_set_tRNS(png_ptr, info_ptr, trans_alpha,
2695 num_trans, trans_color);
2696 trans - array of transparent entries
2697 trans_alpha - array of alpha (transparency)
2698 entries for palette (PNG_INFO_tRNS)
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]2699 trans_color - graylevel or color sample values
2700 (in order red, green, blue) of the
2701 single transparent color for
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]2702 non-paletted images (PNG_INFO_tRNS)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2703 num_trans - number of transparent entries
2704 (PNG_INFO_tRNS)
2705
2706 png_set_hIST(png_ptr, info_ptr, hist);
2707 (PNG_INFO_hIST)
2708 hist - histogram of palette (array of
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2709 png_uint_16)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2710
2711 png_set_tIME(png_ptr, info_ptr, mod_time);
2712 mod_time - time image was last modified
2713 (PNG_VALID_tIME)
2714
2715 png_set_bKGD(png_ptr, info_ptr, background);
2716 background - background color (PNG_VALID_bKGD)
2717
2718 png_set_text(png_ptr, info_ptr, text_ptr, num_text);
2719 text_ptr - array of png_text holding image
2720 comments
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2721 text_ptr[i].compression - type of compression used
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2722 on "text" PNG_TEXT_COMPRESSION_NONE
2723 PNG_TEXT_COMPRESSION_zTXt
2724 PNG_ITXT_COMPRESSION_NONE
2725 PNG_ITXT_COMPRESSION_zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2726 text_ptr[i].key - keyword for comment. Must contain
2727 1-79 characters.
2728 text_ptr[i].text - text comments for current
2729 keyword. Can be NULL or empty.
2730 text_ptr[i].text_length - length of text string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2731 after decompression, 0 for iTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2732 text_ptr[i].itxt_length - length of itxt string,
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2733 after decompression, 0 for tEXt/zTXt
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2734 text_ptr[i].lang - language of comment (NULL or
2735 empty for unknown).
2736 text_ptr[i].translated_keyword - keyword in UTF-8 (NULL
2737 or empty for unknown).
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2738 num_text - number of comments
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2739
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2740 png_set_sPLT(png_ptr, info_ptr, &palette_ptr,
2741 num_spalettes);
2742 palette_ptr - array of png_sPLT_struct structures
2743 to be added to the list of palettes
2744 in the info structure.
2745 num_spalettes - number of palette structures to be
2746 added.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2747
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2748 png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y,
2749 unit_type);
2750 offset_x - positive offset from the left
2751 edge of the screen
2752 offset_y - positive offset from the top
2753 edge of the screen
2754 unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER
2755
2756 png_set_pHYs(png_ptr, info_ptr, res_x, res_y,
2757 unit_type);
2758 res_x - pixels/unit physical resolution
2759 in x direction
2760 res_y - pixels/unit physical resolution
2761 in y direction
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2762 unit_type - PNG_RESOLUTION_UNKNOWN,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2763 PNG_RESOLUTION_METER
2764
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2765 png_set_sCAL(png_ptr, info_ptr, unit, width, height)
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2766 unit - physical scale units (an integer)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2767 width - width of a pixel in physical scale units
2768 height - height of a pixel in physical scale units
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2769 (width and height are doubles)
2770
2771 png_set_sCAL_s(png_ptr, info_ptr, unit, width, height)
2772 unit - physical scale units (an integer)
2773 width - width of a pixel in physical scale units
2774 height - height of a pixel in physical scale units
2775 (width and height are strings like "2.54")
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2776
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2777 png_set_unknown_chunks(png_ptr, info_ptr, &unknowns,
2778 num_unknowns)
2779 unknowns - array of png_unknown_chunk
2780 structures holding unknown chunks
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2781 unknowns[i].name - name of unknown chunk
2782 unknowns[i].data - data of unknown chunk
Glenn Randers-Pehrson4accabb2000-04-14 14:20:47 -0500[diff] [blame]2783 unknowns[i].size - size of unknown chunk's data
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2784 unknowns[i].location - position to write chunk in file
2785 0: do not write chunk
2786 PNG_HAVE_IHDR: before PLTE
2787 PNG_HAVE_PLTE: before IDAT
2788 PNG_AFTER_IDAT: after IDAT
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2789
2790The "location" member is set automatically according to
2791what part of the output file has already been written.
2792You can change its value after calling png_set_unknown_chunks()
2793as demonstrated in pngtest.c. Within each of the "locations",
2794the chunks are sequenced according to their position in the
2795structure (that is, the value of "i", which is the order in which
2796the chunk was either read from the input file or defined with
2797png_set_unknown_chunks).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2798
2799A quick word about text and num_text. text is an array of png_text
2800structures. num_text is the number of valid structures in the array.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2801Each png_text structure holds a language code, a keyword, a text value,
2802and a compression type.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2803
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2804The compression types have the same valid numbers as the compression
2805types of the image data. Currently, the only valid number is zero.
2806However, you can store text either compressed or uncompressed, unlike
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2807images, which always have to be compressed. So if you don't want the
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2808text compressed, set the compression type to PNG_TEXT_COMPRESSION_NONE.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2809Because tEXt and zTXt chunks don't have a language field, if you
2810specify PNG_TEXT_COMPRESSION_NONE or PNG_TEXT_COMPRESSION_zTXt
2811any language code or translated keyword will not be written out.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2812
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2813Until text gets around 1000 bytes, it is not worth compressing it.
2814After the text has been written out to the file, the compression type
2815is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR,
2816so that it isn't written out again at the end (in case you are calling
2817png_write_end() with the same struct.
2818
2819The keywords that are given in the PNG Specification are:
2820
2821 Title Short (one line) title or
2822 caption for image
2823 Author Name of image's creator
2824 Description Description of image (possibly long)
2825 Copyright Copyright notice
2826 Creation Time Time of original image creation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2827 (usually RFC 1123 format, see below)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2828 Software Software used to create the image
2829 Disclaimer Legal disclaimer
2830 Warning Warning of nature of content
2831 Source Device used to create the image
2832 Comment Miscellaneous comment; conversion
2833 from other image format
2834
2835The keyword-text pairs work like this. Keywords should be short
2836simple descriptions of what the comment is about. Some typical
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2837keywords are found in the PNG specification, as is some recommendations
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2838on keywords. You can repeat keywords in a file. You can even write
2839some text before the image and some after. For example, you may want
2840to put a description of the image before the image, but leave the
2841disclaimer until after, so viewers working over modem connections
2842don't have to wait for the disclaimer to go over the modem before
2843they start seeing the image. Finally, keywords should be full
2844words, not abbreviations. Keywords and text are in the ISO 8859-1
2845(Latin-1) character set (a superset of regular ASCII) and can not
2846contain NUL characters, and should not contain control or other
2847unprintable characters. To make the comments widely readable, stick
2848with basic ASCII, and avoid machine specific character set extensions
2849like the IBM-PC character set. The keyword must be present, but
2850you can leave off the text string on non-compressed pairs.
2851Compressed pairs must have a text string, as only the text string
2852is compressed anyway, so the compression would be meaningless.
2853
2854PNG supports modification time via the png_time structure. Two
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2855conversion routines are provided, png_convert_from_time_t() for
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2856time_t and png_convert_from_struct_tm() for struct tm. The
2857time_t routine uses gmtime(). You don't have to use either of
2858these, but if you wish to fill in the png_time structure directly,
2859you should provide the time in universal time (GMT) if possible
2860instead of your local time. Note that the year number is the full
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2861year (e.g. 1998, rather than 98 - PNG is year 2000 compliant!), and
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2862that months start with 1.
2863
2864If you want to store the time of the original image creation, you should
2865use a plain tEXt chunk with the "Creation Time" keyword. This is
2866necessary because the "creation time" of a PNG image is somewhat vague,
2867depending on whether you mean the PNG file, the time the image was
2868created in a non-PNG format, a still photo from which the image was
2869scanned, or possibly the subject matter itself. In order to facilitate
2870machine-readable dates, it is recommended that the "Creation Time"
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2871tEXt 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]2872although this isn't a requirement. Unlike the tIME chunk, the
2873"Creation Time" tEXt chunk is not expected to be automatically changed
2874by the software. To facilitate the use of RFC 1123 dates, a function
2875png_convert_to_rfc1123(png_timep) is provided to convert from PNG
2876time to an RFC 1123 format string.
2877
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2878.SS Writing unknown chunks
2879
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2880You can use the png_set_unknown_chunks function to queue up chunks
2881for writing. You give it a chunk name, raw data, and a size; that's
2882all there is to it. The chunks will be written by the next following
2883png_write_info_before_PLTE, png_write_info, or png_write_end function.
2884Any chunks previously read into the info structure's unknown-chunk
2885list will also be written out in a sequence that satisfies the PNG
2886specification's ordering rules.
2887
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2888.SS The high-level write interface
2889
2890At this point there are two ways to proceed; through the high-level
2891write interface, or through a sequence of low-level write operations.
2892You can use the high-level interface if your image data is present
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]2893in the info structure. All defined output
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]2894transformations are permitted, enabled by the following masks.
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2895
2896 PNG_TRANSFORM_IDENTITY No transformation
2897 PNG_TRANSFORM_PACKING Pack 1, 2 and 4-bit samples
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2898 PNG_TRANSFORM_PACKSWAP Change order of packed
2899 pixels to LSB first
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2900 PNG_TRANSFORM_INVERT_MONO Invert monochrome images
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]2901 PNG_TRANSFORM_SHIFT Normalize pixels to the
2902 sBIT depth
2903 PNG_TRANSFORM_BGR Flip RGB to BGR, RGBA
2904 to BGRA
2905 PNG_TRANSFORM_SWAP_ALPHA Flip RGBA to ARGB or GA
2906 to AG
2907 PNG_TRANSFORM_INVERT_ALPHA Change alpha from opacity
2908 to transparency
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2909 PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples
Glenn Randers-Pehrson1eb14e92008-12-10 07:14:45 -0600[diff] [blame]2910 PNG_TRANSFORM_STRIP_FILLER Strip out filler
2911 bytes (deprecated).
2912 PNG_TRANSFORM_STRIP_FILLER_BEFORE Strip out leading
2913 filler bytes
2914 PNG_TRANSFORM_STRIP_FILLER_AFTER Strip out trailing
2915 filler bytes
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2916
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]2917If you have valid image data in the info structure (you can use
2918png_set_rows() to put image data in the info structure), simply do this:
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2919
2920 png_write_png(png_ptr, info_ptr, png_transforms, NULL)
2921
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]2922where png_transforms is an integer containing the bitwise OR of some set of
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2923transformation flags. This call is equivalent to png_write_info(),
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2924followed the set of transformations indicated by the transform mask,
2925then png_write_image(), and finally png_write_end().
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2926
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]2927(The final parameter of this call is not yet used. Someday it might point
2928to transformation parameters required by some future output transform.)
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2929
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]2930You must use png_transforms and not call any png_set_transform() functions
2931when you use png_write_png().
2932
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2933.SS The low-level write interface
2934
2935If you are going the low-level route instead, you are now ready to
2936write all the file information up to the actual image data. You do
2937this with a call to png_write_info().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2938
2939 png_write_info(png_ptr, info_ptr);
2940
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]2941Note that there is one transformation you may need to do before
2942png_write_info(). In PNG files, the alpha channel in an image is the
2943level of opacity. If your data is supplied as a level of
2944transparency, you can invert the alpha channel before you write it, so
2945that 0 is fully transparent and 255 (in 8-bit or paletted images) or
294665535 (in 16-bit images) is fully opaque, with
2947
2948 png_set_invert_alpha(png_ptr);
2949
2950This must appear before png_write_info() instead of later with the
2951other transformations because in the case of paletted images the tRNS
2952chunk data has to be inverted before the tRNS chunk is written. If
2953your image is not a paletted image, the tRNS data (which in such cases
2954represents a single color to be rendered as transparent) won't need to
2955be changed, and you can safely do this transformation after your
2956png_write_info() call.
2957
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2958If you need to write a private chunk that you want to appear before
2959the PLTE chunk when PLTE is present, you can write the PNG info in
2960two steps, and insert code to write your own chunk between them:
2961
2962 png_write_info_before_PLTE(png_ptr, info_ptr);
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]2963 png_set_unknown_chunks(png_ptr, info_ptr, ...);
Glenn Randers-Pehrson5379b241999-11-27 10:22:33 -0600[diff] [blame]2964 png_write_info(png_ptr, info_ptr);
2965
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2966After you've written the file information, you can set up the library
2967to handle any special transformations of the image data. The various
2968ways to transform the data will be described in the order that they
2969should occur. This is important, as some of these change the color
2970type and/or bit depth of the data, and some others only work on
2971certain color types and bit depths. Even though each transformation
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]2972checks 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]2973make sure to only enable a transformation if it will be valid for the
2974data. For example, don't swap red and blue on grayscale data.
2975
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]2976PNG files store RGB pixels packed into 3 or 6 bytes. This code tells
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]2977the 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]2978to 3 or 6 bytes (or strip 2 or 4-byte grayscale+filler data to 1 or 2
2979bytes per pixel).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2980
2981 png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
2982
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]2983where the 0 is unused, and the location is either PNG_FILLER_BEFORE or
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2984PNG_FILLER_AFTER, depending upon whether the filler byte in the pixel
2985is stored XRGB or RGBX.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2986
2987PNG files pack pixels of bit depths 1, 2, and 4 into bytes as small as
2988they can, resulting in, for example, 8 pixels per byte for 1 bit files.
2989If the data is supplied at 1 pixel per byte, use this code, which will
2990correctly pack the pixels into a single byte:
2991
2992 png_set_packing(png_ptr);
2993
2994PNG files reduce possible bit depths to 1, 2, 4, 8, and 16. If your
2995data is of another bit depth, you can write an sBIT chunk into the
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]2996file so that decoders can recover the original data if desired.
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]2997
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]2998 /* Set the true bit depth of the image data */
2999 if (color_type & PNG_COLOR_MASK_COLOR)
3000 {
3001 sig_bit.red = true_bit_depth;
3002 sig_bit.green = true_bit_depth;
3003 sig_bit.blue = true_bit_depth;
3004 }
3005 else
3006 {
3007 sig_bit.gray = true_bit_depth;
3008 }
3009 if (color_type & PNG_COLOR_MASK_ALPHA)
3010 {
3011 sig_bit.alpha = true_bit_depth;
3012 }
3013
3014 png_set_sBIT(png_ptr, info_ptr, &sig_bit);
3015
3016If 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]3017one 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]3018this will scale the values to appear to be the correct bit depth as
3019is required by PNG.
3020
3021 png_set_shift(png_ptr, &sig_bit);
3022
3023PNG files store 16 bit pixels in network byte order (big-endian,
3024ie. most significant bits first). This code would be used if they are
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3025supplied the other way (little-endian, i.e. least significant bits
3026first, the way PCs store them):
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3027
3028 if (bit_depth > 8)
3029 png_set_swap(png_ptr);
3030
3031If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you
3032need to change the order the pixels are packed into bytes, you can use:
3033
3034 if (bit_depth < 8)
3035 png_set_packswap(png_ptr);
3036
3037PNG files store 3 color pixels in red, green, blue order. This code
3038would be used if they are supplied as blue, green, red:
3039
3040 png_set_bgr(png_ptr);
3041
3042PNG files describe monochrome as black being zero and white being
3043one. This code would be used if the pixels are supplied with this reversed
3044(black being one and white being zero):
3045
3046 png_set_invert_mono(png_ptr);
3047
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3048Finally, you can write your own transformation function if none of
3049the existing ones meets your needs. This is done by setting a callback
3050with
3051
3052 png_set_write_user_transform_fn(png_ptr,
3053 write_transform_fn);
3054
3055You must supply the function
3056
3057 void write_transform_fn(png_ptr ptr, row_info_ptr
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3058 row_info, png_bytep data)
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3059
3060See pngtest.c for a working example. Your function will be called
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3061before any of the other transformations are processed.
3062
3063You can also set up a pointer to a user structure for use by your
3064callback function.
3065
3066 png_set_user_transform_info(png_ptr, user_ptr, 0, 0);
3067
3068The user_channels and user_depth parameters of this function are ignored
3069when writing; you can set them to zero as shown.
3070
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3071You can retrieve the pointer via the function png_get_user_transform_ptr().
3072For example:
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3073
3074 voidp write_user_transform_ptr =
3075 png_get_user_transform_ptr(png_ptr);
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3076
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3077It is possible to have libpng flush any pending output, either manually,
3078or automatically after a certain number of lines have been written. To
3079flush the output stream a single time call:
3080
3081 png_write_flush(png_ptr);
3082
3083and to have libpng flush the output stream periodically after a certain
3084number of scanlines have been written, call:
3085
3086 png_set_flush(png_ptr, nrows);
3087
3088Note that the distance between rows is from the last time png_write_flush()
3089was called, or the first row of the image if it has never been called.
3090So if you write 50 lines, and then png_set_flush 25, it will flush the
3091output on the next scanline, and every 25 lines thereafter, unless
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3092png_write_flush() is called before 25 more lines have been written.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3093If 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]3094RGB image) the image compression may decrease noticeably (although this
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3095may be acceptable for real-time applications). Infrequent flushing will
3096only degrade the compression performance by a few percent over images
3097that do not use flushing.
3098
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3099.SS Writing the image data
3100
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3101That's it for the transformations. Now you can write the image data.
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3102The 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]3103whole image in memory, you can just call png_write_image() and libpng
3104will write the image. You will need to pass in an array of pointers to
3105each row. This function automatically handles interlacing, so you don't
3106need to call png_set_interlace_handling() or call this function multiple
3107times, or any of that other stuff necessary with png_write_rows().
3108
3109 png_write_image(png_ptr, row_pointers);
3110
3111where row_pointers is:
3112
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3113 png_byte *row_pointers[height];
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3114
3115You can point to void or char or whatever you use for pixels.
3116
Glenn Randers-Pehrson896239b1998-04-21 15:03:57 -0500[diff] [blame]3117If you don't want to write the whole image at once, you can
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3118use png_write_rows() instead. If the file is not interlaced,
3119this is simple:
3120
3121 png_write_rows(png_ptr, row_pointers,
3122 number_of_rows);
3123
3124row_pointers is the same as in the png_write_image() call.
3125
3126If 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]3127a single row_pointer instead of an array of row_pointers:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3128
3129 png_bytep row_pointer = row;
3130
Glenn Randers-Pehrson520a7642000-03-21 05:13:06 -0600[diff] [blame]3131 png_write_row(png_ptr, row_pointer);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3132
3133When the file is interlaced, things can get a good deal more
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3134complicated. The only currently (as of the PNG Specification
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3135version 1.2, dated July 1999) defined interlacing scheme for PNG files
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3136is the "Adam7" interlace scheme, that breaks down an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3137image into seven smaller images of varying size. libpng will build
3138these images for you, or you can do them yourself. If you want to
3139build them yourself, see the PNG specification for details of which
3140pixels to write when.
3141
3142If you don't want libpng to handle the interlacing details, just
3143use png_set_interlace_handling() and call png_write_rows() the
3144correct number of times to write all seven sub-images.
3145
3146If you want libpng to build the sub-images, call this before you start
3147writing any rows:
3148
3149 number_of_passes =
3150 png_set_interlace_handling(png_ptr);
3151
3152This will return the number of passes needed. Currently, this
3153is seven, but may change if another interlace type is added.
3154
3155Then write the complete image number_of_passes times.
3156
3157 png_write_rows(png_ptr, row_pointers,
3158 number_of_rows);
3159
3160As some of these rows are not used, and thus return immediately,
3161you may want to read about interlacing in the PNG specification,
3162and only update the rows that are actually used.
3163
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3164.SS Finishing a sequential write
3165
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3166After you are finished writing the image, you should finish writing
3167the file. If you are interested in writing comments or time, you should
3168pass an appropriately filled png_info pointer. If you are not interested,
3169you can pass NULL.
3170
3171 png_write_end(png_ptr, info_ptr);
3172
3173When you are done, you can free all memory used by libpng like this:
3174
3175 png_destroy_write_struct(&png_ptr, &info_ptr);
3176
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3177It is also possible to individually free the info_ptr members that
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3178point to libpng-allocated storage with the following function:
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3179
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3180 png_free_data(png_ptr, info_ptr, mask, seq)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3181 mask - identifies data to be freed, a mask
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3182 containing the bitwise OR of one or
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3183 more of
3184 PNG_FREE_PLTE, PNG_FREE_TRNS,
3185 PNG_FREE_HIST, PNG_FREE_ICCP,
3186 PNG_FREE_PCAL, PNG_FREE_ROWS,
3187 PNG_FREE_SCAL, PNG_FREE_SPLT,
3188 PNG_FREE_TEXT, PNG_FREE_UNKN,
3189 or simply PNG_FREE_ALL
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3190 seq - sequence number of item to be freed
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3191 (-1 for all items)
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3192
Glenn Randers-Pehrsonfc4a1432000-05-17 17:39:34 -0500[diff] [blame]3193This function may be safely called when the relevant storage has
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3194already been freed, or has not yet been allocated, or was allocated
3195by the user and not by libpng, and will in those
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3196cases do nothing. The "seq" parameter is ignored if only one item
3197of the selected data type, such as PLTE, is allowed. If "seq" is not
Glenn Randers-Pehrson68ea2432000-04-01 21:10:05 -0600[diff] [blame]3198-1, and multiple items are allowed for the data type identified in
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3199the mask, such as text or sPLT, only the n'th item in the structure
3200is freed, where n is "seq".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3201
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3202If you allocated data such as a palette that you passed
3203in to libpng with png_set_*, you must not free it until just before the call to
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3204png_destroy_write_struct().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3205
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3206The default behavior is only to free data that was allocated internally
3207by libpng. This can be changed, so that libpng will not free the data,
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3208or so that it will free data that was allocated by the user with png_malloc()
3209or png_zalloc() and passed in via a png_set_*() function, with
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3210
3211 png_data_freer(png_ptr, info_ptr, freer, mask)
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3212 mask - which data elements are affected
3213 same choices as in png_free_data()
3214 freer - one of
3215 PNG_DESTROY_WILL_FREE_DATA
3216 PNG_SET_WILL_FREE_DATA
3217 PNG_USER_WILL_FREE_DATA
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3218
3219For example, to transfer responsibility for some data from a read structure
3220to a write structure, you could use
3221
3222 png_data_freer(read_ptr, read_info_ptr,
3223 PNG_USER_WILL_FREE_DATA,
3224 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3225 png_data_freer(write_ptr, write_info_ptr,
3226 PNG_DESTROY_WILL_FREE_DATA,
3227 PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST)
3228
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3229thereby briefly reassigning responsibility for freeing to the user but
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3230immediately afterwards reassigning it once more to the write_destroy
3231function. Having done this, it would then be safe to destroy the read
3232structure and continue to use the PLTE, tRNS, and hIST data in the write
3233structure.
3234
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3235This function only affects data that has already been allocated.
3236You can call this function before calling after the png_set_*() functions
3237to control whether the user or png_destroy_*() is supposed to free the data.
3238When the user assumes responsibility for libpng-allocated data, the
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3239application must use
3240png_free() to free it, and when the user transfers responsibility to libpng
3241for data that the user has allocated, the user must have used png_malloc()
3242or png_zalloc() to allocate it.
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3243
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3244If you allocated text_ptr.text, text_ptr.lang, and text_ptr.translated_keyword
3245separately, do not transfer responsibility for freeing text_ptr to libpng,
3246because when libpng fills a png_text structure it combines these members with
3247the key member, and png_free_data() will free only text_ptr.key. Similarly,
3248if you transfer responsibility for free'ing text_ptr from libpng to your
3249application, your application must not separately free those members.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3250For a more compact example of writing a PNG image, see the file example.c.
3251
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3252.SH V. Modifying/Customizing libpng:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3253
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3254There are two issues here. The first is changing how libpng does
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3255standard things like memory allocation, input/output, and error handling.
3256The second deals with more complicated things like adding new chunks,
3257adding new transformations, and generally changing how libpng works.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3258Both of those are compile-time issues; that is, they are generally
3259determined at the time the code is written, and there is rarely a need
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3260to provide the user with a means of changing them.
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3261
3262Memory allocation, input/output, and error handling
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3263
3264All of the memory allocation, input/output, and error handling in libpng
Glenn Randers-Pehrson231e6872001-01-12 15:13:06 -0600[diff] [blame]3265goes through callbacks that are user-settable. The default routines are
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3266in pngmem.c, pngrio.c, pngwio.c, and pngerror.c, respectively. To change
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3267these functions, call the appropriate png_set_*_fn() function.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3268
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3269Memory allocation is done through the functions png_malloc()
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3270and png_free(). These currently just call the standard C functions. If
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3271your pointers can't access more then 64K at a time, you will want to set
3272MAXSEG_64K in zlib.h. Since it is unlikely that the method of handling
3273memory allocation on a platform will change between applications, these
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3274functions must be modified in the library at compile time. If you prefer
3275to use a different method of allocating and freeing data, you can use
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3276png_create_read_struct_2() or png_create_write_struct_2() to register
3277your own functions as described above.
Glenn Randers-Pehrsoncfbed9b2002-05-21 18:06:08 -0500[diff] [blame]3278These functions also provide a void pointer that can be retrieved via
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3279
3280 mem_ptr=png_get_mem_ptr(png_ptr);
3281
3282Your replacement memory functions must have prototypes as follows:
3283
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3284 png_voidp malloc_fn(png_structp png_ptr,
Glenn Randers-Pehrsonae498dc2001-11-24 14:53:31 -0600[diff] [blame]3285 png_size_t size);
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3286 void free_fn(png_structp png_ptr, png_voidp ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3287
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]3288Your malloc_fn() must return NULL in case of failure. The png_malloc()
3289function will normally call png_error() if it receives a NULL from the
3290system memory allocator or from your replacement malloc_fn().
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]3291
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3292Your free_fn() will never be called with a NULL ptr, since libpng's
3293png_free() checks for NULL before calling free_fn().
3294
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3295Input/Output in libpng is done through png_read() and png_write(),
3296which currently just call fread() and fwrite(). The FILE * is stored in
3297png_struct and is initialized via png_init_io(). If you wish to change
3298the method of I/O, the library supplies callbacks that you can set
3299through the function png_set_read_fn() and png_set_write_fn() at run
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3300time, instead of calling the png_init_io() function. These functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3301also provide a void pointer that can be retrieved via the function
3302png_get_io_ptr(). For example:
3303
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3304 png_set_read_fn(png_structp read_ptr,
3305 voidp read_io_ptr, png_rw_ptr read_data_fn)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3306
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3307 png_set_write_fn(png_structp write_ptr,
3308 voidp write_io_ptr, png_rw_ptr write_data_fn,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3309 png_flush_ptr output_flush_fn);
3310
Glenn Randers-Pehrsonf7d1a171998-06-06 15:31:35 -0500[diff] [blame]3311 voidp read_io_ptr = png_get_io_ptr(read_ptr);
3312 voidp write_io_ptr = png_get_io_ptr(write_ptr);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3313
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3314The replacement I/O functions must have prototypes as follows:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3315
3316 void user_read_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3317 png_bytep data, png_size_t length);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3318 void user_write_data(png_structp png_ptr,
Glenn Randers-Pehrson837a3d12002-05-10 20:19:58 -0500[diff] [blame]3319 png_bytep data, png_size_t length);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3320 void user_flush_data(png_structp png_ptr);
3321
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3322The user_read_data() function is responsible for detecting and
3323handling end-of-data errors.
3324
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3325Supplying NULL for the read, write, or flush functions sets them back
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3326to using the default C stream functions, which expect the io_ptr to
3327point to a standard *FILE structure. It is probably a mistake
3328to use NULL for one of write_data_fn and output_flush_fn but not both
3329of them, unless you have built libpng with PNG_NO_WRITE_FLUSH defined.
3330It is an error to read from a write stream, and vice versa.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3331
3332Error handling in libpng is done through png_error() and png_warning().
3333Errors handled through png_error() are fatal, meaning that png_error()
3334should never return to its caller. Currently, this is handled via
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3335setjmp() and longjmp() (unless you have compiled libpng with
3336PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()),
3337but you could change this to do things like exit() if you should wish.
3338
3339On non-fatal errors, png_warning() is called
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3340to print a warning message, and then control returns to the calling code.
3341By default png_error() and png_warning() print a message on stderr via
Glenn Randers-Pehrson38e6e772000-04-09 19:06:13 -0500[diff] [blame]3342fprintf() unless the library is compiled with PNG_NO_CONSOLE_IO defined
3343(because you don't want the messages) or PNG_NO_STDIO defined (because
3344fprintf() isn't available). If you wish to change the behavior of the error
3345functions, you will need to set up your own message callbacks. These
3346functions are normally supplied at the time that the png_struct is created.
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3347It is also possible to redirect errors and warnings to your own replacement
3348functions after png_create_*_struct() has been called by calling:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3349
3350 png_set_error_fn(png_structp png_ptr,
3351 png_voidp error_ptr, png_error_ptr error_fn,
3352 png_error_ptr warning_fn);
3353
3354 png_voidp error_ptr = png_get_error_ptr(png_ptr);
3355
3356If NULL is supplied for either error_fn or warning_fn, then the libpng
3357default function will be used, calling fprintf() and/or longjmp() if a
3358problem is encountered. The replacement error functions should have
3359parameters as follows:
3360
3361 void user_error_fn(png_structp png_ptr,
3362 png_const_charp error_msg);
3363 void user_warning_fn(png_structp png_ptr,
3364 png_const_charp warning_msg);
3365
3366The motivation behind using setjmp() and longjmp() is the C++ throw and
3367catch exception handling methods. This makes the code much easier to write,
3368as there is no need to check every return code of every function call.
3369However, there are some uncertainties about the status of local variables
3370after a longjmp, so the user may want to be careful about doing anything after
3371setjmp returns non-zero besides returning itself. Consult your compiler
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3372documentation for more details. For an alternative approach, you may wish
3373to use the "cexcept" facility (see http://cexcept.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3374
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3375.SS Custom chunks
3376
3377If you need to read or write custom chunks, you may need to get deeper
3378into the libpng code. The library now has mechanisms for storing
3379and writing chunks of unknown type; you can even declare callbacks
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]3380for custom chunks. However, this may not be good enough if the
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3381library code itself needs to know about interactions between your
3382chunk and existing `intrinsic' chunks.
3383
3384If you need to write a new intrinsic chunk, first read the PNG
3385specification. Acquire a first level of
3386understanding of how it works. Pay particular attention to the
3387sections that describe chunk names, and look at how other chunks were
3388designed, so you can do things similarly. Second, check out the
3389sections of libpng that read and write chunks. Try to find a chunk
3390that is similar to yours and use it as a template. More details can
3391be found in the comments inside the code. It is best to handle unknown
3392chunks in a generic method, via callback functions, instead of by
3393modifying libpng functions.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3394
3395If you wish to write your own transformation for the data, look through
3396the part of the code that does the transformations, and check out some of
3397the simpler ones to get an idea of how they work. Try to find a similar
3398transformation to the one you want to add and copy off of it. More details
3399can be found in the comments inside the code itself.
3400
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3401.SS Configuring for 16 bit platforms
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3402
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3403You 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]3404it 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]3405won'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]3406
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3407.SS Configuring for DOS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3408
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3409For DOS users who only have access to the lower 640K, you will
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3410have to limit zlib's memory usage via a png_set_compression_mem_level()
3411call. See zlib.h or zconf.h in the zlib library for more information.
3412
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3413.SS Configuring for Medium Model
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3414
3415Libpng's support for medium model has been tested on most of the popular
3416compilers. Make sure MAXSEG_64K gets defined, USE_FAR_KEYWORD gets
3417defined, and FAR gets defined to far in pngconf.h, and you should be
3418all set. Everything in the library (except for zlib's structure) is
3419expecting far data. You must use the typedefs with the p or pp on
3420the end for pointers (or at least look at them and be careful). Make
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3421note that the rows of data are defined as png_bytepp, which is an
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3422unsigned char far * far *.
3423
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3424.SS Configuring for gui/windowing platforms:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3425
3426You will need to write new error and warning functions that use the GUI
3427interface, as described previously, and set them to be the error and
Glenn Randers-Pehrsona77ef622000-02-18 13:48:52 -0600[diff] [blame]3428warning functions at the time that png_create_*_struct() is called,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3429in order to have them available during the structure initialization.
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3430They can be changed later via png_set_error_fn(). On some compilers,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3431you may also have to change the memory allocators (png_malloc, etc.).
3432
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3433.SS Configuring for compiler xxx:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3434
Glenn Randers-Pehrsonbeb572e2006-08-19 13:59:24 -0500[diff] [blame]3435All includes for libpng are in pngconf.h. If you need to add, change
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3436or delete an include, this is the place to do it.
3437The includes that are not needed outside libpng are placed in pngpriv.h,
3438which is only used by the routines inside libpng itself.
3439The files in libpng proper only include pngpriv.h and png.h, which
3440in turn includes pngconf.h.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3441
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3442.SS Configuring zlib:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3443
3444There are special functions to configure the compression. Perhaps the
3445most useful one changes the compression level, which currently uses
3446input compression values in the range 0 - 9. The library normally
3447uses the default compression level (Z_DEFAULT_COMPRESSION = 6). Tests
3448have shown that for a large majority of images, compression values in
3449the range 3-6 compress nearly as well as higher levels, and do so much
3450faster. For online applications it may be desirable to have maximum speed
3451(Z_BEST_SPEED = 1). With versions of zlib after v0.99, you can also
3452specify no compression (Z_NO_COMPRESSION = 0), but this would create
3453files larger than just storing the raw bitmap. You can specify the
3454compression level by calling:
3455
3456 png_set_compression_level(png_ptr, level);
3457
3458Another useful one is to reduce the memory level used by the library.
3459The memory level defaults to 8, but it can be lowered if you are
3460short on memory (running DOS, for example, where you only have 640K).
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3461Note that the memory level does have an effect on compression; among
3462other things, lower levels will result in sections of incompressible
3463data being emitted in smaller stored blocks, with a correspondingly
3464larger relative overhead of up to 15% in the worst case.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3465
3466 png_set_compression_mem_level(png_ptr, level);
3467
3468The other functions are for configuring zlib. They are not recommended
3469for normal use and may result in writing an invalid PNG file. See
3470zlib.h for more information on what these mean.
3471
3472 png_set_compression_strategy(png_ptr,
3473 strategy);
3474 png_set_compression_window_bits(png_ptr,
3475 window_bits);
3476 png_set_compression_method(png_ptr, method);
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3477 png_set_compression_buffer_size(png_ptr, size);
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3478
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3479.SS Controlling row filtering
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3480
3481If you want to control whether libpng uses filtering or not, which
3482filters are used, and how it goes about picking row filters, you
3483can call one of these functions. The selection and configuration
3484of row filters can have a significant impact on the size and
3485encoding speed and a somewhat lesser impact on the decoding speed
3486of an image. Filtering is enabled by default for RGB and grayscale
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3487images (with and without alpha), but not for paletted images nor
3488for any images with bit depths less than 8 bits/pixel.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3489
3490The 'method' parameter sets the main filtering method, which is
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]3491currently only '0' in the PNG 1.2 specification. The 'filters'
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3492parameter sets which filter(s), if any, should be used for each
3493scanline. Possible values are PNG_ALL_FILTERS and PNG_NO_FILTERS
3494to turn filtering on and off, respectively.
3495
3496Individual filter types are PNG_FILTER_NONE, PNG_FILTER_SUB,
3497PNG_FILTER_UP, PNG_FILTER_AVG, PNG_FILTER_PAETH, which can be bitwise
Glenn Randers-Pehrson6942d532000-05-01 09:31:54 -0500[diff] [blame]3498ORed together with '|' to specify one or more filters to use.
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3499These filters are described in more detail in the PNG specification.
3500If you intend to change the filter type during the course of writing
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3501the image, you should start with flags set for all of the filters
3502you intend to use so that libpng can initialize its internal
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3503structures appropriately for all of the filter types. (Note that this
3504means the first row must always be adaptively filtered, because libpng
3505currently does not allocate the filter buffers until png_write_row()
3506is called for the first time.)
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3507
3508 filters = PNG_FILTER_NONE | PNG_FILTER_SUB
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3509 PNG_FILTER_UP | PNG_FILTER_AVG |
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3510 PNG_FILTER_PAETH | PNG_ALL_FILTERS;
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3511
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3512 png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE,
3513 filters);
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]3514 The second parameter can also be
3515 PNG_INTRAPIXEL_DIFFERENCING if you are
3516 writing a PNG to be embedded in a MNG
3517 datastream. This parameter must be the
3518 same as the value of filter_method used
3519 in png_set_IHDR().
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3520
3521It is also possible to influence how libpng chooses from among the
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3522available filters. This is done in one or both of two ways - by
3523telling it how important it is to keep the same filter for successive
3524rows, and by telling it the relative computational costs of the filters.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3525
3526 double weights[3] = {1.5, 1.3, 1.1},
3527 costs[PNG_FILTER_VALUE_LAST] =
3528 {1.0, 1.3, 1.3, 1.5, 1.7};
3529
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]3530 png_set_filter_heuristics(png_ptr,
3531 PNG_FILTER_HEURISTIC_WEIGHTED, 3,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3532 weights, costs);
3533
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3534The weights are multiplying factors that indicate to libpng that the
3535row filter should be the same for successive rows unless another row filter
3536is that many times better than the previous filter. In the above example,
3537if 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]3538"sum of absolute differences" 1.5 x 1.3 times higher than other filters
3539and still be chosen, while the NONE filter could have a sum 1.1 times
3540higher than other filters and still be chosen. Unspecified weights are
3541taken to be 1.0, and the specified weights should probably be declining
3542like those above in order to emphasize recent filters over older filters.
3543
3544The filter costs specify for each filter type a relative decoding cost
3545to be considered when selecting row filters. This means that filters
3546with higher costs are less likely to be chosen over filters with lower
3547costs, unless their "sum of absolute differences" is that much smaller.
3548The costs do not necessarily reflect the exact computational speeds of
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]3549the various filters, since this would unduly influence the final image
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3550size.
3551
3552Note that the numbers above were invented purely for this example and
3553are given only to help explain the function usage. Little testing has
3554been done to find optimum values for either the costs or the weights.
3555
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3556.SS Removing unwanted object code
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3557
3558There are a bunch of #define's in pngconf.h that control what parts of
3559libpng are compiled. All the defines end in _SUPPORTED. If you are
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3560never going to use a capability, you can change the #define to #undef
3561before recompiling libpng and save yourself code and data space, or
3562you can turn off individual capabilities with defines that begin with
3563PNG_NO_.
3564
3565You can also turn all of the transforms and ancillary chunk capabilities
Glenn Randers-Pehrson228bd392000-04-23 23:14:02 -0500[diff] [blame]3566off en masse with compiler directives that define
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3567PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS,
3568or all four,
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3569along with directives to turn on any of the capabilities that you do
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3570want. The PNG_NO_READ[or WRITE]_TRANSFORMS directives disable
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3571the extra transformations but still leave the library fully capable of reading
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]3572and writing PNG files with all known public chunks
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3573Use of the PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS directive
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3574produces a library that is incapable of reading or writing ancillary chunks.
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3575If you are not using the progressive reading capability, you can
Glenn Randers-Pehrsond0dce401998-05-09 10:02:29 -0500[diff] [blame]3576turn that off with PNG_NO_PROGRESSIVE_READ (don't confuse
Glenn Randers-Pehrson08a33431998-03-07 06:06:55 -0600[diff] [blame]3577this with the INTERLACING capability, which you'll still have).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3578
3579All the reading and writing specific code are in separate files, so the
3580linker should only grab the files it needs. However, if you want to
3581make sure, or if you are building a stand alone library, all the
3582reading files start with pngr and all the writing files start with
3583pngw. The files that don't match either (like png.c, pngtrans.c, etc.)
3584are used for both reading and writing, and always need to be included.
3585The progressive reader is in pngpread.c
3586
3587If you are creating or distributing a dynamically linked library (a .so
3588or DLL file), you should not remove or disable any parts of the library,
3589as this will cause applications linked with different versions of the
3590library to fail if they call functions not available in your library.
3591The size of the library itself should not be an issue, because only
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3592those sections that are actually used will be loaded into memory.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3593
Glenn Randers-Pehrson61c32d92000-02-04 23:40:16 -0600[diff] [blame]3594.SS Requesting debug printout
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3595
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3596The macro definition PNG_DEBUG can be used to request debugging
3597printout. Set it to an integer value in the range 0 to 3. Higher
3598numbers result in increasing amounts of debugging information. The
3599information is printed to the "stderr" file, unless another file
3600name is specified in the PNG_DEBUG_FILE macro definition.
3601
3602When PNG_DEBUG > 0, the following functions (macros) become available:
3603
3604 png_debug(level, message)
3605 png_debug1(level, message, p1)
3606 png_debug2(level, message, p1, p2)
3607
3608in which "level" is compared to PNG_DEBUG to decide whether to print
3609the message, "message" is the formatted string to be printed,
3610and p1 and p2 are parameters that are to be embedded in the string
3611according to printf-style formatting directives. For example,
3612
3613 png_debug1(2, "foo=%d\n", foo);
3614
3615is expanded to
3616
3617 if(PNG_DEBUG > 2)
3618 fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo);
3619
3620When PNG_DEBUG is defined but is zero, the macros aren't defined, but you
3621can still use PNG_DEBUG to control your own debugging:
3622
3623 #ifdef PNG_DEBUG
3624 fprintf(stderr, ...
3625 #endif
3626
3627When PNG_DEBUG = 1, the macros are defined, but only png_debug statements
3628having level = 0 will be printed. There aren't any such statements in
3629this version of libpng, but if you insert some they will be printed.
3630
Glenn Randers-Pehrson56f63962008-10-06 10:16:17 -0500[diff] [blame]3631.SH VI. MNG support
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3632
3633The MNG specification (available at http://www.libpng.org/pub/mng) allows
3634certain extensions to PNG for PNG images that are embedded in MNG datastreams.
3635Libpng can support some of these extensions. To enable them, use the
3636png_permit_mng_features() function:
3637
3638 feature_set = png_permit_mng_features(png_ptr, mask)
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3639 mask is a png_uint_32 containing the bitwise OR of the
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3640 features you want to enable. These include
3641 PNG_FLAG_MNG_EMPTY_PLTE
3642 PNG_FLAG_MNG_FILTER_64
3643 PNG_ALL_MNG_FEATURES
Glenn Randers-Pehrsonebd7f9a2006-10-19 09:37:56 -0500[diff] [blame]3644 feature_set is a png_uint_32 that is the bitwise AND of
Glenn Randers-Pehrson2ad31ae2000-12-15 08:54:42 -0600[diff] [blame]3645 your mask with the set of MNG features that is
3646 supported by the version of libpng that you are using.
3647
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3648It is an error to use this function when reading or writing a standalone
3649PNG file with the PNG 8-byte signature. The PNG datastream must be wrapped
Glenn Randers-Pehrsonf05f8032000-12-23 14:27:39 -0600[diff] [blame]3650in a MNG datastream. As a minimum, it must have the MNG 8-byte signature
3651and the MHDR and MEND chunks. Libpng does not provide support for these
3652or any other MNG chunks; your application must provide its own support for
3653them. You may wish to consider using libmng (available at
3654http://www.libmng.com) instead.
Glenn Randers-Pehrson408b4212000-12-18 09:33:57 -0600[diff] [blame]3655
Glenn Randers-Pehrson8fb550c2009-03-21 08:15:32 -0500[diff] [blame]3656.SH VII. Changes to Libpng from version 0.88
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3657
3658It should be noted that versions of libpng later than 0.96 are not
3659distributed by the original libpng author, Guy Schalnat, nor by
3660Andreas Dilger, who had taken over from Guy during 1996 and 1997, and
3661distributed versions 0.89 through 0.96, but rather by another member
3662of the original PNG Group, Glenn Randers-Pehrson. Guy and Andreas are
3663still alive and well, but they have moved on to other things.
3664
3665The old libpng functions png_read_init(), png_write_init(),
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]3666png_info_init(), png_read_destroy(), and png_write_destroy() have been
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3667moved to PNG_INTERNAL in version 0.95 to discourage their use. These
3668functions will be removed from libpng version 2.0.0.
3669
3670The preferred method of creating and initializing the libpng structures is
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3671via the png_create_read_struct(), png_create_write_struct(), and
3672png_create_info_struct() because they isolate the size of the structures
3673from the application, allow version error checking, and also allow the
3674use of custom error handling routines during the initialization, which
3675the old functions do not. The functions png_read_destroy() and
3676png_write_destroy() do not actually free the memory that libpng
3677allocated for these structs, but just reset the data structures, so they
3678can be used instead of png_destroy_read_struct() and
3679png_destroy_write_struct() if you feel there is too much system overhead
3680allocating and freeing the png_struct for each image read.
3681
3682Setting the error callbacks via png_set_message_fn() before
3683png_read_init() as was suggested in libpng-0.88 is no longer supported
Glenn Randers-Pehrson5c6aeb21998-12-29 11:47:59 -0600[diff] [blame]3684because this caused applications that do not use custom error functions
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3685to fail if the png_ptr was not initialized to zero. It is still possible
3686to set the error callbacks AFTER png_read_init(), or to change them with
Glenn Randers-Pehrson75294572000-05-06 14:09:57 -0500[diff] [blame]3687png_set_error_fn(), which is essentially the same function, but with a new
3688name to force compilation errors with applications that try to use the old
3689method.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]3690
Glenn Randers-Pehrson1ef65b62000-05-12 06:19:53 -0500[diff] [blame]3691Starting with version 1.0.7, you can find out which version of the library
3692you are using at run-time:
3693
3694 png_uint_32 libpng_vn = png_access_version_number();
3695
3696The number libpng_vn is constructed from the major version, minor
3697version with leading zero, and release number with leading zero,
3698(e.g., libpng_vn for version 1.0.7 is 10007).
3699
3700You can also check which version of png.h you used when compiling your
3701application:
3702
3703 png_uint_32 application_vn = PNG_LIBPNG_VER;
3704
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]3705.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]3706
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]3707Support for user memory management was enabled by default. To
3708accomplish this, the functions png_create_read_struct_2(),
3709png_create_write_struct_2(), png_set_mem_fn(), png_get_mem_ptr(),
3710png_malloc_default(), and png_free_default() were added.
3711
3712Support for certain MNG features was enabled.
3713
3714Support for numbered error messages was added. However, we never got
3715around to actually numbering the error messages. The function
3716png_set_strip_error_numbers() was added (Note: the prototype for this
3717function was inadvertently removed from png.h in PNG_NO_ASSEMBLER_CODE
3718builds of libpng-1.2.15. It was restored in libpng-1.2.36).
3719
3720The png_malloc_warn() function was added at libpng-1.2.3. This issues
3721a png_warning and returns NULL instead of aborting when it fails to
3722acquire the requested memory allocation.
3723
3724Support for setting user limits on image width and height was enabled
3725by default. The functions png_set_user_limits(), png_get_user_width_max(),
3726and png_get_user_height_max() were added at libpng-1.2.6.
3727
3728The png_set_add_alpha() function was added at libpng-1.2.7.
3729
3730The function png_set_expand_gray_1_2_4_to_8() was added at libpng-1.2.9.
3731Unlike png_set_gray_1_2_4_to_8(), the new function does not expand the
3732tRNS chunk to alpha. The png_set_gray_1_2_4_to_8() function is
3733deprecated.
3734
3735A number of macro definitions in support of runtime selection of
3736assembler code features (especially Intel MMX code support) were
3737added at libpng-1.2.0:
3738
3739 PNG_ASM_FLAG_MMX_SUPPORT_COMPILED
3740 PNG_ASM_FLAG_MMX_SUPPORT_IN_CPU
3741 PNG_ASM_FLAG_MMX_READ_COMBINE_ROW
3742 PNG_ASM_FLAG_MMX_READ_INTERLACE
3743 PNG_ASM_FLAG_MMX_READ_FILTER_SUB
3744 PNG_ASM_FLAG_MMX_READ_FILTER_UP
3745 PNG_ASM_FLAG_MMX_READ_FILTER_AVG
3746 PNG_ASM_FLAG_MMX_READ_FILTER_PAETH
3747 PNG_ASM_FLAGS_INITIALIZED
3748 PNG_MMX_READ_FLAGS
3749 PNG_MMX_FLAGS
3750 PNG_MMX_WRITE_FLAGS
3751 PNG_MMX_FLAGS
3752
3753We added the following functions in support of runtime
3754selection of assembler code features:
3755
3756 png_get_mmx_flagmask()
3757 png_set_mmx_thresholds()
3758 png_get_asm_flags()
3759 png_get_mmx_bitdepth_threshold()
3760 png_get_mmx_rowbytes_threshold()
3761 png_set_asm_flags()
3762
3763We replaced all of these functions with simple stubs in libpng-1.2.20,
3764when the Intel assembler code was removed due to a licensing issue.
3765
3766.SH IX. Changes to Libpng from version 1.0.x/1.2.x to 1.4.x
3767
3768Private libpng prototypes and macro definitions were moved from
3769png.h and pngconf.h into a new pngpriv.h header file.
3770
3771Support for the iTXt chunk has been enabled by default.
3772
3773Support for global arrays was disabled by default.
3774
3775Some obsolete/deprecated macros and functions have been removed.
3776
Glenn Randers-Pehrson3d893a02009-08-31 13:32:46 -0500[diff] [blame^]3777These macros are deprecated:
3778
3779 PNG_READ_TRANSFORMS_NOT_SUPPORTED
3780 PNG_PROGRESSIVE_READ_NOT_SUPPORTED
3781 PNG_NO_SEQUENTIAL_READ_SUPPORTED
3782 PNG_WRITE_TRANSFORMS_NOT_SUPPORTED
3783 PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED
3784 PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED
3785
3786They have been replaced, respectively, by:
3787
3788 PNG_NO_READ_TRANSFORMS
3789 PNG_NO_PROGRESSIVE_READ
3790 PNG_NO_SEQUENTIAL_READ
3791 PNG_NO_WRITE_TRANSFORMS
3792 PNG_NO_READ_ANCILLARY_CHUNKS
3793 PNG_NO_WRITE_ANCILLARY_CHUNKS
3794
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]3795The PNG_1_0_X and PNG_1_2_X macros were eliminated.
3796
Glenn Randers-Pehrsonbc7156d2009-07-06 09:11:54 -0500[diff] [blame]3797The PNG_LEGACY_SUPPORTED macro was eliminated.
3798
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]3799Many WIN32_WCE #ifdefs were removed.
3800
3801PNG_MAX_UINT was replaced with PNG_UINT_31_MAX. It has been
3802deprecated since libpng-1.0.16 and libpng-1.2.6.
3803
3804The function
3805 png_check_sig(sig, num)
3806was replaced with
3807 !png_sig_cmp(sig, 0, num)
3808It has been deprecated since libpng-0.90.
3809
3810The functions png_read_init(info_ptr), png_write_init(info_ptr),
3811png_info_init(info_ptr), png_read_destroy(), and png_write_destroy()
3812have been removed. They have been deprecated since libpng-0.95.
3813
3814The function
3815 png_set_gray_1_2_4_to_8()
3816which also expands tRNS to alpha was replaced with
3817 png_set_expand_gray_1_2_4_to_8()
3818which does not. It has been deprecated since libpng-1.0.18 and 1.2.9.
3819
3820Support for numbered error messages was removed by default, since we
3821never got around to actually numbering the error messages. The function
3822png_set_strip_error_numbers() was removed from the library by default.
3823
3824Functions png_set_benign_errors(), png_benign_error(), and
3825png_chunk_benign_error() were added.
3826
3827Support for setting the maximum amount of memory that the application
3828will allocate for reading chunks was added, as a security measure.
3829The functions png_set_chunk_cache_max() and png_get_chunk_cache_max()
3830were added to the library.
3831
3832We implemented support for I/O states. Added png_ptr member io_state, and
3833functions png_get_io_chunk_name() and png_get_io_state() in pngget.c
3834
3835The png_permit_empty_plte() was removed. It has been deprecated
3836since libpng-1.0.9. Use png_permit_mng_features() instead.
3837
3838We removed the obsolete stub functions png_get_mmx_flagmask(),
3839png_set_mmx_thresholds(), png_get_asm_flags(),
3840png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(),
3841png_set_asm_flags(), and png_mmx_supported()
3842
3843We removed the png_memcpy_check() and png_memset_check() functions.
3844
3845We changed the prototype for png_malloc() from
3846 png_malloc(png_structp png_ptr, png_uint_32 size)
3847to
3848 png_malloc(png_structp png_ptr, png_alloc_size_t size)
3849
3850We changed the prototypes of png_get_compression_buffer_size() and
3851png_set_compression_buffer_size() to work with png_size_t instead of
3852png_uint_32.
3853
3854The png_zalloc() function no longer zeroes out the memory that it
3855allocates.
3856
3857The png_zalloc() and png_zfree() functions are no longer exported.
3858
3859The png_calloc() function was added.
3860
3861We removed the trailing '.' from the warning and error messages.
3862
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]3863We added PNG_TRANSFORM_GRAY_TO_RGB to the available high-level
3864input transforms.
3865
Glenn Randers-Pehrson866b62a2009-08-08 16:33:14 -0500[diff] [blame]3866The png_struct and info_struct members "trans" and "trans_values" were
3867changed to "trans_alpha" and "trans_color", respectively.
3868
Glenn Randers-Pehrsonbc7156d2009-07-06 09:11:54 -0500[diff] [blame]3869The call to png_do_chop() in pngrtran.c, which reduces 16-bit input
3870files to 8-bit bit depth, was relocated ahead of the building
3871of gamma tables. This allows us to build 8-bit tables instead
3872of 16-bit tables, when only 8-bit tables are needed. This avoids
3873wasting some computing resources when the application has called
3874the png_set_strip_16() function and encounters a 16-bit PNG file.
Glenn Randers-Pehrson6a9c2ce2009-03-27 19:30:10 -0500[diff] [blame]3875
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3876.SH X. Detecting libpng
3877
3878The png_get_io_ptr() function has been present since libpng-0.88, has never
3879changed, and is unaffected by conditional compilation macros. It is the
3880best choice for use in configure scripts for detecting the presence of any
Glenn Randers-Pehrson99708d52009-06-29 17:30:00 -0500[diff] [blame]3881libpng version since 0.88. In an autoconf "configure.in" you could use
3882
3883 AC_CHECK_LIB(png, png_get_io_ptr, ...
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3884
3885.SH XI. Source code repository
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3886
3887Since about February 2009, version 1.2.34, libpng has been under "git" source
3888control. The git repository was built from old libpng-x.y.z.tar.gz files
3889going back to version 0.70. You can access the git repository (read only)
3890at
3891
3892 git://libpng.git.sourceforge.net/gitroot/libpng
3893
3894or you can browse it via "gitweb" at
3895
3896 http://libpng.git.sourceforge.net/git/gitweb.cgi?p=libpng
3897
3898Patches can be sent to glennrp at users.sourceforge.net or to
3899png-mng-implement at lists.sourceforge.net or you can upload them to
3900the libpng bug tracker at
3901
3902 http://libpng.sourceforge.net
3903
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]3904.SH XII. Coding style
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3905
3906Our coding style is similar to the "Allman" style, with curly
3907braces on separate lines:
3908
3909 if (condition)
3910 {
3911 action;
3912 }
3913
3914 else if (another condition)
3915 {
3916 another action;
3917 }
3918
3919The braces can be omitted from simple one-line actions:
3920
3921 if (condition)
3922 return (0);
3923
3924We use 3-space indentation, except for continued statements which
3925are usually indented the same as the first line of the statement
3926plus four more spaces.
3927
3928Comments appear with the leading "/*" at the same indentation as
3929the statement that follows the comment:
3930
3931 /* Single-line comment */
3932 statement;
3933
3934 /* Multiple-line
3935 * comment
3936 */
3937 statement;
3938
3939Very short comments can be placed at the end of the statement
3940to which they pertain:
3941
3942 statement; /* comment */
3943
3944We don't use C++ style ("//") comments. We have, however,
3945used them in the past in some now-abandoned MMX assembler
3946code.
3947
Glenn Randers-Pehrsonb5444a12009-06-08 08:36:19 -0500[diff] [blame]3948Functions and their curly braces are not indented, and
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3949exported functions are marked with PNGAPI:
3950
3951 /* This is a public function that is visible to
3952 * application programers. It does thus-and-so.
3953 */
3954 void PNGAPI
3955 png_exported_function(png_ptr, png_info, foo)
3956 {
3957 body;
3958 }
3959
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]3960The prototypes for all exported functions appear in png.h,
3961above the comment that says
3962
3963 /* Maintainer: Put new public prototypes here ... */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3964
3965We mark all non-exported functions with "/* PRIVATE */"":
3966
3967 void /* PRIVATE */
3968 png_non_exported_function(png_ptr, png_info, foo)
3969 {
3970 body;
3971 }
3972
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]3973The prototypes for non-exported functions (except for those in
3974pngtest) appear in
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]3975pngpriv.h
Glenn Randers-Pehrson416976f2009-07-27 22:16:09 -0500[diff] [blame]3976above the comment that says
3977
3978 /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3979
3980The names of all exported functions and variables begin
3981with "png_", and all publicly visible C preprocessor
3982macros begin with "PNG_".
3983
3984We put a space after each comma and after each semicolon
3985in "for" statments, and we put spaces before and after each
3986C binary operator and after "for" or "while". We don't
3987put a space between a typecast and the expression being
3988cast, nor do we put one between a function name and the
3989left parenthesis that follows it:
3990
3991 for (i = 2; i > 0; --i)
3992 x[i] = a(x) + (int)b;
3993
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]3994We prefer #ifdef and #ifndef to #if defined() and if !defined()
3995when there is only one macro being tested.
3996
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]3997Other rules can be inferred by inspecting the libpng
3998source.
3999
Glenn Randers-Pehrson424c9852009-06-02 13:45:15 -0500[diff] [blame]4000.SH XIII. Y2K Compliance in libpng
Glenn Randers-Pehrson76546822009-05-16 07:25:42 -0500[diff] [blame]4001
Glenn Randers-Pehrson77d0cde2009-08-31 11:18:25 -0500[diff] [blame]4002August 31, 2009
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4003
4004Since the PNG Development group is an ad-hoc body, we can't make
4005an official declaration.
4006
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4007This is your unofficial assurance that libpng from version 0.71 and
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]4008upward through 1.4.0beta79 are Y2K compliant. It is my belief that earlier
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4009versions were also Y2K compliant.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4010
4011Libpng only has three year fields. One is a 2-byte unsigned integer that
4012will hold years up to 65535. The other two hold the date in text
4013format, and will hold years up to 9999.
4014
4015The integer is
4016 "png_uint_16 year" in png_time_struct.
4017
4018The strings are
4019 "png_charp time_buffer" in png_struct and
4020 "near_time_buffer", which is a local character string in png.c.
4021
4022There are seven time-related functions:
4023
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]4024 png_convert_to_rfc_1123() in png.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4025 (formerly png_convert_to_rfc_1152() in error)
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4026 png_convert_from_struct_tm() in pngwrite.c, called
4027 in pngwrite.c
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4028 png_convert_from_time_t() in pngwrite.c
4029 png_get_tIME() in pngget.c
4030 png_handle_tIME() in pngrutil.c, called in pngread.c
4031 png_set_tIME() in pngset.c
4032 png_write_tIME() in pngwutil.c, called in pngwrite.c
4033
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]4034All appear to handle dates properly in a Y2K environment. The
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4035png_convert_from_time_t() function calls gmtime() to convert from system
4036clock time, which returns (year - 1900), which we properly convert to
4037the full 4-digit year. There is a possibility that applications using
4038libpng are not passing 4-digit years into the png_convert_to_rfc_1123()
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4039function, or that they are incorrectly passing only a 2-digit year
4040instead of "year - 1900" into the png_convert_from_struct_tm() function,
4041but this is not under our control. The libpng documentation has always
4042stated that it works with 4-digit years, and the APIs have been
4043documented as such.
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4044
4045The tIME chunk itself is also Y2K compliant. It uses a 2-byte unsigned
4046integer to hold the year, and can hold years as large as 65535.
4047
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4048zlib, upon which libpng depends, is also Y2K compliant. It contains
4049no date-related code.
4050
Glenn Randers-Pehrson87544ac1999-01-13 22:06:39 -0600[diff] [blame]4051
4052 Glenn Randers-Pehrson
4053 libpng maintainer
4054 PNG Development Group
4055
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4056.SH NOTE
4057
4058Note about libpng version numbers:
4059
4060Due to various miscommunications, unforeseen code incompatibilities
4061and occasional factors outside the authors' control, version numbering
4062on the library has not always been consistent and straightforward.
4063The following table summarizes matters since version 0.89c, which was
4064the first widely used release:
4065
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4066 source png.h png.h shared-lib
4067 version string int version
4068 ------- ------ ----- ----------
4069 0.89c ("beta 3") 0.89 89 1.0.89
4070 0.90 ("beta 4") 0.90 90 0.90
4071 0.95 ("beta 5") 0.95 95 0.95
4072 0.96 ("beta 6") 0.96 96 0.96
4073 0.97b ("beta 7") 1.00.97 97 1.0.1
4074 0.97c 0.97 97 2.0.97
4075 0.98 0.98 98 2.0.98
4076 0.99 0.99 98 2.0.99
4077 0.99a-m 0.99 99 2.0.99
4078 1.00 1.00 100 2.1.0
4079 1.0.0 1.0.0 100 2.1.0
4080 1.0.0 (from here on, the 100 2.1.0
4081 1.0.1 png.h string is 10001 2.1.0
4082 1.0.1a-e identical to the 10002 from here on, the
4083 1.0.2 source version) 10002 shared library is 2.V
4084 1.0.2a-b 10003 where V is the source
4085 1.0.1 10001 code version except as
4086 1.0.1a-e 10002 2.1.0.1a-e noted.
4087 1.0.2 10002 2.1.0.2
4088 1.0.2a-b 10003 2.1.0.2a-b
4089 1.0.3 10003 2.1.0.3
4090 1.0.3a-d 10004 2.1.0.3a-d
4091 1.0.4 10004 2.1.0.4
4092 1.0.4a-f 10005 2.1.0.4a-f
4093 1.0.5 (+ 2 patches) 10005 2.1.0.5
4094 1.0.5a-d 10006 2.1.0.5a-d
4095 1.0.5e-r 10100 2.1.0.5e-r
4096 1.0.5s-v 10006 2.1.0.5s-v
4097 1.0.6 (+ 3 patches) 10006 2.1.0.6
4098 1.0.6d-g 10007 2.1.0.6d-g
4099 1.0.6h 10007 10.6h
4100 1.0.6i 10007 10.6i
4101 1.0.6j 10007 2.1.0.6j
4102 1.0.7beta11-14 DLLNUM 10007 2.1.0.7beta11-14
4103 1.0.7beta15-18 1 10007 2.1.0.7beta15-18
4104 1.0.7rc1-2 1 10007 2.1.0.7rc1-2
4105 1.0.7 1 10007 2.1.0.7
4106 1.0.8beta1-4 1 10008 2.1.0.8beta1-4
4107 1.0.8rc1 1 10008 2.1.0.8rc1
4108 1.0.8 1 10008 2.1.0.8
4109 1.0.9beta1-6 1 10009 2.1.0.9beta1-6
4110 1.0.9rc1 1 10009 2.1.0.9rc1
4111 1.0.9beta7-10 1 10009 2.1.0.9beta7-10
4112 1.0.9rc2 1 10009 2.1.0.9rc2
4113 1.0.9 1 10009 2.1.0.9
Glenn Randers-Pehrsone1644472001-03-23 05:06:56 -0600[diff] [blame]4114 1.0.10beta1 1 10010 2.1.0.10beta1
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4115 1.0.10rc1 1 10010 2.1.0.10rc1
Glenn Randers-Pehrson13cfbac2001-03-30 06:42:28 -0600[diff] [blame]4116 1.0.10 1 10010 2.1.0.10
Glenn Randers-Pehrsone1eff582001-04-14 20:15:41 -0500[diff] [blame]4117 1.0.11beta1-3 1 10011 2.1.0.11beta1-3
Glenn Randers-Pehrson82ae3832001-04-20 10:32:10 -0500[diff] [blame]4118 1.0.11rc1 1 10011 2.1.0.11rc1
Glenn Randers-Pehrson32835392001-04-27 08:29:32 -0500[diff] [blame]4119 1.0.11 1 10011 2.1.0.11
Glenn Randers-Pehrsonb1828932001-06-23 08:03:17 -0500[diff] [blame]4120 1.0.12beta1-2 2 10012 2.1.0.12beta1-2
4121 1.0.12rc1 2 10012 2.1.0.12rc1
4122 1.0.12 2 10012 2.1.0.12
4123 1.1.0a-f - 10100 2.1.1.0a-f abandoned
Glenn Randers-Pehrson8b6a8892001-05-18 04:54:50 -0500[diff] [blame]4124 1.2.0beta1-2 2 10200 2.1.2.0beta1-2
Glenn Randers-Pehrson5a0be342001-10-18 20:55:13 -0500[diff] [blame]4125 1.2.0beta3-5 3 10200 3.1.2.0beta3-5
4126 1.2.0rc1 3 10200 3.1.2.0rc1
4127 1.2.0 3 10200 3.1.2.0
Glenn Randers-Pehrson5cded0b2001-11-07 07:10:08 -0600[diff] [blame]4128 1.2.1beta-4 3 10201 3.1.2.1beta1-4
Glenn Randers-Pehrsondb3b88d2001-12-04 06:30:43 -0600[diff] [blame]4129 1.2.1rc1-2 3 10201 3.1.2.1rc1-2
4130 1.2.1 3 10201 3.1.2.1
Glenn Randers-Pehrson25228ab2002-03-31 07:33:55 -0600[diff] [blame]4131 1.2.2beta1-6 12 10202 12.so.0.1.2.2beta1-6
Glenn Randers-Pehrsonfcbd7872002-04-07 16:35:38 -0500[diff] [blame]4132 1.0.13beta1 10 10013 10.so.0.1.0.13beta1
4133 1.0.13rc1 10 10013 10.so.0.1.0.13rc1
4134 1.2.2rc1 12 10202 12.so.0.1.2.2rc1
Glenn Randers-Pehrson4fb046a2002-04-15 09:25:51 -0500[diff] [blame]4135 1.0.13 10 10013 10.so.0.1.0.13
4136 1.2.2 12 10202 12.so.0.1.2.2
Glenn Randers-Pehrson22f28962002-05-13 18:17:09 -0500[diff] [blame]4137 1.2.3rc1-6 12 10203 12.so.0.1.2.3rc1-6
4138 1.2.3 12 10203 12.so.0.1.2.3
Glenn Randers-Pehrsond020e9d2002-06-28 09:34:00 -0500[diff] [blame]4139 1.2.4beta1-3 13 10204 12.so.0.1.2.4beta1-3
Glenn Randers-Pehrson2ae022d2002-07-01 22:23:46 -0500[diff] [blame]4140 1.2.4rc1 13 10204 12.so.0.1.2.4rc1
Glenn Randers-Pehrson484a8a12002-07-07 19:15:20 -0500[diff] [blame]4141 1.0.14 10 10014 10.so.0.1.0.14
4142 1.2.4 13 10204 12.so.0.1.2.4
Glenn Randers-Pehrson5b5dcf82004-07-17 22:45:44 -0500[diff] [blame]4143 1.2.5beta1-2 13 10205 12.so.0.1.2.5beta1-2
4144 1.0.15rc1 10 10015 10.so.0.1.0.15rc1
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4145 1.0.15 10 10015 10.so.0.1.0.15
4146 1.2.5 13 10205 12.so.0.1.2.5
4147 1.2.6beta1-4 13 10206 12.so.0.1.2.6beta1-4
Glenn Randers-Pehrson37f116a2004-08-15 07:15:39 -0500[diff] [blame]4148 1.2.6rc1-5 13 10206 12.so.0.1.2.6rc1-5
4149 1.0.16 10 10016 10.so.0.1.0.16
4150 1.2.6 13 10206 12.so.0.1.2.6
Glenn Randers-Pehrson67864af2004-08-28 23:30:07 -0500[diff] [blame]4151 1.2.7beta1-2 13 10207 12.so.0.1.2.7beta1-2
Glenn Randers-Pehrson5b779162004-09-04 13:25:08 -0500[diff] [blame]4152 1.0.17rc1 10 10017 12.so.0.1.0.17rc1
4153 1.2.7rc1 13 10207 12.so.0.1.2.7rc1
Glenn Randers-Pehrson250dfe12004-09-11 21:19:54 -0500[diff] [blame]4154 1.0.17 10 10017 12.so.0.1.0.17
4155 1.2.7 13 10207 12.so.0.1.2.7
Glenn Randers-Pehrson40936072004-11-20 11:18:40 -0600[diff] [blame]4156 1.2.8beta1-5 13 10208 12.so.0.1.2.8beta1-5
Glenn Randers-Pehrson584b96e2004-11-29 15:08:00 -0600[diff] [blame]4157 1.0.18rc1-5 10 10018 12.so.0.1.0.18rc1-5
4158 1.2.8rc1-5 13 10208 12.so.0.1.2.8rc1-5
Glenn Randers-Pehrson917648e2004-12-02 18:14:51 -0600[diff] [blame]4159 1.0.18 10 10018 12.so.0.1.0.18
4160 1.2.8 13 10208 12.so.0.1.2.8
Glenn Randers-Pehrsone6474622006-03-04 16:50:47 -0600[diff] [blame]4161 1.2.9beta1-3 13 10209 12.so.0.1.2.9beta1-3
Glenn Randers-Pehrson4deeb792006-03-22 16:21:59 -0600[diff] [blame]4162 1.2.9beta4-11 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrson3a512032006-03-31 05:29:33 -0600[diff] [blame]4163 1.2.9rc1 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsona7d0c942006-04-14 06:22:52 -0500[diff] [blame]4164 1.2.9 13 10209 12.so.0.9[.0]
Glenn Randers-Pehrsond60b8fa2006-04-20 21:31:14 -0500[diff] [blame]4165 1.2.10beta1-7 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson17218292006-04-20 07:20:46 -0500[diff] [blame]4166 1.2.10rc1-2 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson86dc9812006-05-10 07:27:44 -0500[diff] [blame]4167 1.2.10 13 10210 12.so.0.10[.0]
Glenn Randers-Pehrson6bc53be2006-06-16 07:52:03 -0500[diff] [blame]4168 1.4.0beta1-6 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsond60c8862009-06-15 21:56:14 -0500[diff] [blame]4169 1.2.11beta1-4 13 10210 12.so.0.11[.0]
Glenn Randers-Pehrson3424ee72006-07-12 13:33:47 -0500[diff] [blame]4170 1.4.0beta7-8 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrson701dbaa2006-11-17 09:36:54 -0600[diff] [blame]4171 1.2.11 13 10211 12.so.0.11[.0]
4172 1.2.12 13 10212 12.so.0.12[.0]
4173 1.4.0beta9-14 14 10400 14.so.0.0[.0]
4174 1.2.13 13 10213 12.so.0.13[.0]
Glenn Randers-Pehrson97a9b482008-10-25 20:03:28 -0500[diff] [blame]4175 1.4.0beta15-36 14 10400 14.so.0.0[.0]
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]4176 1.4.0beta37-79 14 10400 14.so.14.0[.0]
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4177
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4178Henceforth the source version will match the shared-library minor
4179and patch numbers; the shared-library major version number will be
4180used for changes in backward compatibility, as it is intended. The
4181PNG_PNGLIB_VER macro, which is not used within libpng but is available
4182for applications, is an unsigned integer of the form xyyzz corresponding
4183to 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]4184were given the previous public release number plus a letter, until
4185version 1.0.6j; from then on they were given the upcoming public
4186release number plus "betaNN" or "rcN".
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]4187
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4188.SH "SEE ALSO"
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4189libpngpf(3), png(5)
4190.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4191.IR libpng :
4192.IP
Glenn Randers-Pehrsona4981d42004-08-25 22:00:45 -0500[diff] [blame]4193http://libpng.sourceforge.net (follow the [DOWNLOAD] link)
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]4194http://www.libpng.org/pub/png
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4195
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4196.LP
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4197.IR zlib :
4198.IP
4199(generally) at the same location as
4200.I libpng
4201or at
4202.br
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]4203ftp://ftp.info-zip.org/pub/infozip/zlib
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4204
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4205.LP
4206.IR PNG specification: RFC 2083
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4207.IP
4208(generally) at the same location as
4209.I libpng
4210or at
4211.br
4212ftp://ds.internic.net/rfc/rfc2083.txt
4213.br
4214or (as a W3C Recommendation) at
4215.br
4216http://www.w3.org/TR/REC-png.html
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4217
Glenn Randers-Pehrsoncbe52d81998-02-28 07:00:24 -0600[diff] [blame]4218.LP
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4219In the case of any inconsistency between the PNG specification
4220and this library, the specification takes precedence.
4221
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4222.SH AUTHORS
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4223This man page: Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]4224<glennrp at users.sourceforge.net>
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4225
4226The contributing authors would like to thank all those who helped
4227with testing, bug fixes, and patience. This wouldn't have been
4228possible without all of you.
4229
4230Thanks to Frank J. T. Wojcik for helping with the documentation.
Glenn Randers-Pehrson166c5a31999-12-10 09:43:02 -0600[diff] [blame]4231
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]4232Libpng version 1.4.0beta79 - August 31, 2009:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4233Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc.
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]4234Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net).
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4235
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4236Supported by the PNG development group
4237.br
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]4238png-mng-implement at lists.sf.net
4239(subscription required; visit
Glenn Randers-Pehrson7b34df32006-02-24 06:30:16 -0600[diff] [blame]4240png-mng-implement at lists.sourceforge.net (subscription required; visit
Glenn Randers-Pehrson9c3ab682006-02-20 22:09:05 -0600[diff] [blame]4241https://lists.sourceforge.net/lists/listinfo/png-mng-implement
4242to subscribe).
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4243
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4244.SH COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4245
Glenn Randers-Pehrson5e5c1e12000-11-10 12:26:19 -0600[diff] [blame]4246(This copy of the libpng notices is provided for your convenience. In case of
4247any discrepancy between this copy and the notices in the file png.h that is
4248included in the libpng distribution, the latter shall prevail.)
4249
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4250If you modify libpng you may insert additional notices immediately following
4251this sentence.
4252
Glenn Randers-Pehrsonbfbf8652009-06-26 21:46:52 -0500[diff] [blame]4253This code is released under the libpng license.
Glenn Randers-Pehrson037023b2009-06-24 10:27:36 -0500[diff] [blame]4254
Glenn Randers-Pehrsonc31d7172009-08-31 11:24:27 -0500[diff] [blame]4255libpng versions 1.2.6, August 15, 2004, through 1.4.0beta79, August 31, 2009, are
Glenn Randers-Pehrsona7dbcba2007-05-15 16:16:34 -0500[diff] [blame]4256Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4257distributed according to the same disclaimer and license as libpng-1.2.5
Glenn Randers-Pehrsond029a752004-08-09 21:50:32 -0500[diff] [blame]4258with the following individual added to the list of Contributing Authors
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4259
4260 Cosmin Truta
Glenn Randers-Pehrson5fea36f2004-07-28 08:20:44 -0500[diff] [blame]4261
4262libpng 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]4263Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
Glenn Randers-Pehrson32fc5ce2000-07-24 06:34:14 -0500[diff] [blame]4264distributed according to the same disclaimer and license as libpng-1.0.6
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4265with the following individuals added to the list of Contributing Authors
4266
4267 Simon-Pierre Cadieux
4268 Eric S. Raymond
4269 Gilles Vollant
4270
4271and with the following additions to the disclaimer:
4272
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]4273 There is no warranty against interference with your
4274 enjoyment of the library or against infringement.
4275 There is no warranty that our efforts or the library
4276 will fulfill any of your particular purposes or needs.
4277 This library is provided with all faults, and the entire
4278 risk of satisfactory quality, performance, accuracy, and
4279 effort is with the user.
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4280
4281libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
4282Copyright (c) 1998, 1999 Glenn Randers-Pehrson
4283Distributed according to the same disclaimer and license as libpng-0.96,
4284with the following individuals added to the list of Contributing Authors:
4285
4286 Tom Lane
4287 Glenn Randers-Pehrson
4288 Willem van Schaik
4289
4290libpng versions 0.89, June 1996, through 0.96, May 1997, are
Glenn Randers-Pehrson54a066a1999-09-19 06:04:18 -0500[diff] [blame]4291Copyright (c) 1996, 1997 Andreas Dilger
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4292Distributed according to the same disclaimer and license as libpng-0.88,
4293with the following individuals added to the list of Contributing Authors:
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4294
4295 John Bowler
4296 Kevin Bracey
4297 Sam Bushell
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4298 Magnus Holmgren
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4299 Greg Roelofs
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4300 Tom Tanner
4301
4302libpng versions 0.5, May 1995, through 0.88, January 1996, are
4303Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
4304
4305For the purposes of this copyright and license, "Contributing Authors"
4306is defined as the following set of individuals:
4307
4308 Andreas Dilger
4309 Dave Martindale
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4310 Guy Eric Schalnat
4311 Paul Schmidt
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4312 Tim Wegner
Glenn Randers-Pehrsonc9442291999-01-06 21:50:16 -0600[diff] [blame]4313
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4314The PNG Reference Library is supplied "AS IS". The Contributing Authors
4315and Group 42, Inc. disclaim all warranties, expressed or implied,
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4316including, without limitation, the warranties of merchantability and of
4317fitness for any purpose. The Contributing Authors and Group 42, Inc.
4318assume no liability for direct, indirect, incidental, special, exemplary,
4319or consequential damages, which may result from the use of the PNG
4320Reference Library, even if advised of the possibility of such damage.
Glenn Randers-Pehrsona357b991998-02-08 20:56:40 -0600[diff] [blame]4321
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4322Permission is hereby granted to use, copy, modify, and distribute this
4323source code, or portions hereof, for any purpose, without fee, subject
4324to the following restrictions:
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4325
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]43261. The origin of this source code must not be misrepresented.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4327
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]43282. Altered versions must be plainly marked as such and
4329 must not be misrepresented as being the original source.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4330
Glenn Randers-Pehrson19095602001-03-14 07:08:39 -0600[diff] [blame]43313. This Copyright notice may not be removed or altered from
4332 any source or altered source distribution.
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4333
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4334The Contributing Authors and Group 42, Inc. specifically permit, without
4335fee, and encourage the use of this source code as a component to
4336supporting the PNG file format in commercial products. If you use this
4337source code in a product, acknowledgment is not required but would be
4338appreciated.
4339
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4340
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4341A "png_get_copyright" function is available, for convenient use in "about"
4342boxes and the like:
4343
4344 printf("%s",png_get_copyright(NULL));
4345
4346Also, the PNG logo (in PNG format, of course) is supplied in the
Glenn Randers-Pehrsona4d54bd2000-07-14 08:15:12 -0500[diff] [blame]4347files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
Glenn Randers-Pehrson4393a9a1999-09-17 12:27:26 -0500[diff] [blame]4348
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4349Libpng is OSI Certified Open Source Software. OSI Certified Open Source is a
Glenn Randers-Pehrsonbcfd15d1999-10-01 14:22:25 -0500[diff] [blame]4350certification mark of the Open Source Initiative.
4351
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4352Glenn Randers-Pehrson
Glenn Randers-Pehrson5dd2b8e2004-11-24 07:50:16 -0600[diff] [blame]4353glennrp at users.sourceforge.net
Glenn Randers-Pehrson77d0cde2009-08-31 11:18:25 -0500[diff] [blame]4354August 31, 2009
Glenn Randers-Pehrson3d5a5202000-07-01 15:37:28 -0500[diff] [blame]4355
Glenn Randers-Pehrson0f881d61998-02-07 10:20:57 -0600[diff] [blame]4356.\" end of man page
4357