| README for libpng version 1.6.37 - April 14, 2019 | |
| ================================================= | |
| 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 or if you want UNIX-style line endings in the text | |
| files, or lpng*.7z or lpng*.zip if you want DOS-style line endings. | |
| Version 0.89 was the first official release of libpng. Don't let the | |
| fact that it's the first release fool you. The libpng library has been | |
| in extensive use and testing since mid-1995. 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 < 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 png 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. | |
| **** | |
| 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 include 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->8 bit color | |
| conversion. | |
| 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. | |
| 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 | |
| I have included a general makefile, as well as several machine and | |
| compiler specific ones, but you may have to modify one for your own | |
| needs. | |
| 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 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/commendations to png-mng-implement at | |
| lists.sourceforge.net (subscription 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 required; visit | |
| https://lists.sourceforge.net/lists/listinfo/png-mng-misc to | |
| subscribe). | |
| Files in this distribution: | |
| ANNOUNCE => Announcement of this version, with recent changes | |
| AUTHORS => List of contributing authors | |
| CHANGES => Description of changes between libpng versions | |
| KNOWNBUG => List of known bugs and deficiencies | |
| 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 | |
| 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 => Contains optimized code for the ARM platform | |
| powerpc => Contains optimized code for the PowerPC platform | |
| contrib => Contributions | |
| arm-neon => Optimized code for ARM-NEON platform | |
| powerpc-vsx => Optimized code for POWERPC-VSX platform | |
| examples => Example programs | |
| gregbook => source code for PNG reading and writing, from | |
| Greg Roelofs' "PNG: The Definitive Guide", | |
| O'Reilly, 1999 | |
| libtests => Test programs | |
| mips-msa => Optimized code for MIPS-MSA platform | |
| pngminim => Minimal decoder, encoder, and progressive decoder | |
| programs demonstrating use of pngusr.dfa | |
| pngminus => Simple pnm2png and png2pnm programs | |
| pngsuite => Test images | |
| testpngs | |
| tools => Various tools | |
| visupng => Contains a MSVC workspace for VisualPng | |
| intel => Optimized code for INTEL-SSE2 platform | |
| mips => Optimized code for MIPS platform | |
| projects => Contains project files and workspaces for | |
| building a DLL | |
| owatcom => Contains a WATCOM project for building libpng | |
| visualc71 => Contains a Microsoft Visual C++ (MSVC) | |
| workspace for building libpng and zlib | |
| vstudio => Contains a Microsoft Visual C++ (MSVC) | |
| workspace for building libpng and zlib | |
| scripts => Directory containing scripts for building libpng: | |
| (see scripts/README.txt for the list of 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.) |