| README for libpng version 1.6.40 |
| ================================ |
| |
| See the note about version numbers near the top of `png.h`. |
| See `INSTALL` for instructions on how to install libpng. |
| |
| Libpng comes in several distribution formats. Get `libpng-*.tar.gz` |
| or `libpng-*.tar.xz` if you want UNIX-style line endings in the text |
| files, or `lpng*.7z` or `lpng*.zip` if you want DOS-style line endings. |
| |
| For a detailed description on using libpng, read `libpng-manual.txt`. |
| For examples of libpng in a program, see `example.c` and `pngtest.c`. |
| For usage information and restrictions (what little they are) on libpng, |
| see `png.h`. For a description on using zlib (the compression library |
| used by libpng) and zlib's restrictions, see `zlib.h`. |
| |
| You should use zlib 1.0.4 or later to run this, but it _may_ work with |
| versions as old as zlib 0.95. Even so, there are bugs in older zlib |
| versions which can cause the output of invalid compression streams for |
| some images. |
| |
| You should also note that zlib is a compression library that is useful |
| for more things than just PNG files. You can use zlib as a drop-in |
| replacement for `fread()` and `fwrite()`, if you are so inclined. |
| |
| zlib should be available at the same place that libpng is, or at |
| https://zlib.net . |
| |
| You may also want a copy of the PNG specification. It is available |
| as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find |
| these at http://www.libpng.org/pub/png/pngdocs.html . |
| |
| This code is currently being archived at https://libpng.sourceforge.io |
| in the download area, and at http://libpng.download/src . |
| |
| This release, based in a large way on Glenn's, Guy's and Andreas' |
| earlier work, was created and will be supported by myself and the PNG |
| development group. |
| |
| Send comments, corrections and commendations to `png-mng-implement` |
| at `lists.sourceforge.net`. (Subscription is required; visit |
| https://lists.sourceforge.net/lists/listinfo/png-mng-implement |
| to subscribe.) |
| |
| Send general questions about the PNG specification to `png-mng-misc` |
| at `lists.sourceforge.net`. (Subscription is required; visit |
| https://lists.sourceforge.net/lists/listinfo/png-mng-misc |
| to subscribe.) |
| |
| Historical notes |
| ---------------- |
| |
| The libpng library has been in extensive use and testing since mid-1995. |
| Version 0.89, published a year later, was the first official release. |
| By late 1997, it had finally gotten to the stage where there hadn't |
| been significant changes to the API in some time, and people have a bad |
| feeling about libraries with versions below 1.0. Version 1.0.0 was |
| released in March 1998. |
| |
| Note that some of the changes to the `png_info` structure render this |
| version of the library binary incompatible with libpng-0.89 or |
| earlier versions if you are using a shared library. The type of the |
| `filler` parameter for `png_set_filler()` has changed from `png_byte` |
| to `png_uint_32`, which will affect shared-library applications that |
| use this function. |
| |
| To avoid problems with changes to the internals of the `info_struct`, |
| new APIs have been made available in 0.95 to avoid direct application |
| access to `info_ptr`. These functions are the `png_set_<chunk>` and |
| `png_get_<chunk>` functions. These functions should be used when |
| accessing/storing the `info_struct` data, rather than manipulating it |
| directly, to avoid such problems in the future. |
| |
| It is important to note that the APIs did not make current programs |
| that access the info struct directly incompatible with the new |
| library, through libpng-1.2.x. In libpng-1.4.x, which was meant to |
| be a transitional release, members of the `png_struct` and the |
| `info_struct` can still be accessed, but the compiler will issue a |
| warning about deprecated usage. Since libpng-1.5.0, direct access |
| to these structs is not allowed, and the definitions of the structs |
| reside in private `pngstruct.h` and `pnginfo.h` header files that are |
| not accessible to applications. It is strongly suggested that new |
| programs use the new APIs (as shown in `example.c` and `pngtest.c`), |
| and older programs be converted to the new format, to facilitate |
| upgrades in the future. |
| |
| The additions since 0.89 include the ability to read from a PNG stream |
| which has had some (or all) of the signature bytes read by the calling |
| application. This also allows the reading of embedded PNG streams that |
| do not have the PNG file signature. As well, it is now possible to set |
| the library action on the detection of chunk CRC errors. It is possible |
| to set different actions based on whether the CRC error occurred in a |
| critical or an ancillary chunk. |
| |
| The additions since 0.90 include the ability to compile libpng as a |
| Windows DLL, and new APIs for accessing data in the `info_struct`. |
| Experimental functions included the ability to set weighting and cost |
| factors for row filter selection, direct reads of integers from buffers |
| on big-endian processors that support misaligned data access, faster |
| methods of doing alpha composition, and more accurate 16-to-8 bit color |
| conversion. Some of these experimental functions, such as the weighted |
| filter heuristics, have since been removed. |
| |
| Files included in this distribution |
| ----------------------------------- |
| |
| ANNOUNCE => Announcement of this version, with recent changes |
| AUTHORS => List of contributing authors |
| CHANGES => Description of changes between libpng versions |
| INSTALL => Instructions to install libpng |
| LICENSE => License to use and redistribute libpng |
| README => This file |
| TODO => Things not implemented in the current library |
| TRADEMARK => Trademark information |
| example.c => Example code for using libpng functions |
| libpng.3 => Manual page for libpng (includes libpng-manual.txt) |
| libpng-manual.txt => Description of libpng and its functions |
| libpngpf.3 => Manual page for libpng's private functions (deprecated) |
| png.5 => Manual page for the PNG format |
| png.c => Basic interface functions common to library |
| png.h => Library function and interface declarations (public) |
| pngpriv.h => Library function and interface declarations (private) |
| pngconf.h => System specific library configuration (public) |
| pngstruct.h => png_struct declaration (private) |
| pnginfo.h => png_info struct declaration (private) |
| pngdebug.h => debugging macros (private) |
| pngerror.c => Error/warning message I/O functions |
| pngget.c => Functions for retrieving info from struct |
| pngmem.c => Memory handling functions |
| pngbar.png => PNG logo, 88x31 |
| pngnow.png => PNG logo, 98x31 |
| pngpread.c => Progressive reading functions |
| pngread.c => Read data/helper high-level functions |
| pngrio.c => Lowest-level data read I/O functions |
| pngrtran.c => Read data transformation functions |
| pngrutil.c => Read data utility functions |
| pngset.c => Functions for storing data into the info_struct |
| pngtest.c => Library test program |
| pngtest.png => Library test sample image |
| pngtrans.c => Common data transformation functions |
| pngwio.c => Lowest-level write I/O functions |
| pngwrite.c => High-level write functions |
| pngwtran.c => Write data transformations |
| pngwutil.c => Write utility functions |
| arm/ => Optimized code for the ARM platform |
| intel/ => Optimized code for the INTEL-SSE2 platform |
| mips/ => Optimized code for the MIPS platform |
| powerpc/ => Optimized code for the PowerPC platform |
| ci/ => Scripts for continuous integration |
| contrib/ => External contributions |
| arm-neon/ => Optimized code for the ARM-NEON platform |
| mips-msa/ => Optimized code for the MIPS-MSA platform |
| powerpc-vsx/ => Optimized code for the POWERPC-VSX platform |
| examples/ => Examples of libpng usage |
| gregbook/ => Source code for PNG reading and writing, from |
| "PNG: The Definitive Guide" by Greg Roelofs, |
| O'Reilly, 1999 |
| libtests/ => Test programs |
| oss-fuzz/ => Files used by the OSS-Fuzz project for fuzz-testing |
| libpng |
| pngminim/ => Minimal decoder, encoder, and progressive decoder |
| programs demonstrating the use of pngusr.dfa |
| pngminus/ => Simple pnm2png and png2pnm programs |
| pngsuite/ => Test images |
| testpngs/ => Test images |
| tools/ => Various tools |
| visupng/ => VisualPng, a Windows viewer for PNG images |
| projects/ => Project files and workspaces for various IDEs |
| owatcom/ => OpenWatcom project |
| visualc71/ => Microsoft Visual C++ 7.1 workspace |
| vstudio/ => Microsoft Visual Studio workspace |
| scripts/ => Scripts and makefiles for building libpng |
| (see scripts/README.txt for the complete list) |
| tests/ => Test scripts |
| |
| Good luck, and happy coding! |
| |
| * Cosmin Truta (current maintainer, since 2018) |
| * Glenn Randers-Pehrson (former maintainer, 1998-2018) |
| * Andreas Eric Dilger (former maintainer, 1996-1997) |
| * Guy Eric Schalnat (original author and former maintainer, 1995-1996) |
| (formerly of Group 42, Inc.) |
