| README for libpng version 1.6.34 - September 29, 2017 (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 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. |
| |
| 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/pngdocs.html . |
| |
| This code is currently being archived at libpng.sourceforge.io in the |
| [DOWNLOAD] area, and at http://libpng.download/src . If you |
| can't find it in any of those places, e-mail me, and I'll help you find it. |
| |
| I am not a lawyer, but I believe that the Export Control Classification |
| Number (ECCN) for libpng is EAR99, which means not subject to export |
| controls or International Traffic in Arms Regulations (ITAR) because it |
| is open source, publicly available software, that does not contain any |
| encryption software. See the EAR, paragraphs 734.3(b)(3) and 734.7(b). |
| |
| 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 twenty 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 |
| 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. |
| |
| -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 |
