| README for libpng version 1.6.7 - November 14, 2013 (shared library 16.0) | |
| 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 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 do not make current programs | |
| that access the info struct directly incompatible with the new | |
| library. However, 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. | |
| The changes made to the library, and bugs fixed are based on discussions | |
| on the PNG-implement mailing list and not on material submitted | |
| privately to Guy, Andreas, or Glenn. They will forward any good | |
| suggestions to the list. | |
| 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 will definitely need zlib 1.0.4 or later if you are | |
| taking advantage of the MS-DOS "far" structure allocation for the small | |
| and medium memory models. 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 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/documents/ | |
| This code is currently being archived at libpng.sf.net in the | |
| [DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it | |
| in any of those places, e-mail me, and I'll help you find it. | |
| If you have any code changes, requests, problems, etc., please e-mail | |
| them to me. Also, I'd appreciate any make files or project files, | |
| and any modifications you needed to make to get libpng to compile, | |
| along with a #define variable to tell what compiler/system you are on. | |
| If you needed to add transformations to libpng, or wish libpng would | |
| provide the image in a different way, drop me a note (and code, if | |
| possible), so I can consider supporting the transformation. | |
| Finally, if you get any warning messages when compiling libpng | |
| (note: not zlib), and they are easy to fix, I'd appreciate the | |
| fix. Please mention "libpng" somewhere in the subject line. Thanks. | |
| This release was created and will be supported by myself (of course | |
| based in a large way on Guy's and Andreas' earlier work), 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) or to glennrp at users.sourceforge.net | |
| You can't reach Guy, the original libpng author, at the addresses | |
| given in previous versions of this document. He and Andreas will | |
| read mail addressed to the png-implement list, however. | |
| Please do not send general questions about PNG. Send them to | |
| png-mng-misc at lists.sf.net (subscription required; visit | |
| https://lists.sourceforge.net/lists/listinfo/png-mng-misc to | |
| subscribe). If you have a question about something | |
| in the PNG specification that is related to using libpng, send it | |
| to me. Send me any questions that start with "I was using libpng, | |
| and ...". If in doubt, send questions to me. I'll bounce them | |
| to others, if necessary. | |
| Please do not send suggestions on how to change PNG. We have | |
| been discussing PNG for eighteen years now, and it is official and | |
| finished. If you have suggestions for libpng, however, I'll | |
| gladly listen. Even if your suggestion is not used immediately, | |
| it may be used later. | |
| Files in this distribution: | |
| ANNOUNCE => Announcement of this version, with recent changes | |
| 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 | |
| Y2KINFO => Statement of Y2K compliance | |
| 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 | |
| contrib => Contributions | |
| examples => Example programs | |
| gregbook => source code for PNG reading and writing, from | |
| Greg Roelofs' "PNG: The Definitive Guide", | |
| O'Reilly, 1999 | |
| libtests => Test programs | |
| pngminim => Minimal decoder, encoder, and progressive decoder | |
| programs demonstrating use of pngusr.dfa | |
| pngminus => Simple pnm2png and png2pnm programs | |
| pngsuite => Test images | |
| tools => Various tools | |
| visupng => Contains a MSVC workspace for VisualPng | |
| 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. | |
| -Glenn Randers-Pehrson (current maintainer, since 1998) | |
| Internet: glennrp at users.sourceforge.net | |
| -Andreas Eric Dilger (former maintainer, 1996-1997) | |
| Internet: adilger at enel.ucalgary.ca | |
| Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ | |
| -Guy Eric Schalnat (original author and former maintainer, 1995-1996) | |
| (formerly of Group 42, Inc) | |
| Internet: gschal at infinet.com | |