1README for libpng version 1.5.12 - July 11, 2012 (shared library 15.0) 2See the note about version numbers near the top of png.h 3 4See INSTALL for instructions on how to install libpng. 5 6Libpng comes in several distribution formats. Get libpng-*.tar.gz, 7libpng-*.tar.xz or libpng-*.tar.bz2 if you want UNIX-style line endings 8in the text files, or lpng*.zip if you want DOS-style line endings. 9 10Version 0.89 was the first official release of libpng. Don't let the 11fact that it's the first release fool you. The libpng library has been in 12extensive use and testing since mid-1995. By late 1997 it had 13finally gotten to the stage where there hadn't been significant 14changes to the API in some time, and people have a bad feeling about 15libraries with versions < 1.0. Version 1.0.0 was released in 16March 1998. 17 18**** 19Note that some of the changes to the png_info structure render this 20version of the library binary incompatible with libpng-0.89 or 21earlier versions if you are using a shared library. The type of the 22"filler" parameter for png_set_filler() has changed from png_byte to 23png_uint_32, which will affect shared-library applications that use 24this function. 25 26To avoid problems with changes to the internals of png_info_struct, 27new APIs have been made available in 0.95 to avoid direct application 28access to info_ptr. These functions are the png_set_<chunk> and 29png_get_<chunk> functions. These functions should be used when 30accessing/storing the info_struct data, rather than manipulating it 31directly, to avoid such problems in the future. 32 33It is important to note that the APIs do not make current programs 34that access the info struct directly incompatible with the new 35library. However, it is strongly suggested that new programs use 36the new APIs (as shown in example.c and pngtest.c), and older programs 37be converted to the new format, to facilitate upgrades in the future. 38**** 39 40Additions since 0.90 include the ability to compile libpng as a 41Windows DLL, and new APIs for accessing data in the info struct. 42Experimental functions include the ability to set weighting and cost 43factors for row filter selection, direct reads of integers from buffers 44on big-endian processors that support misaligned data access, faster 45methods of doing alpha composition, and more accurate 16->8 bit color 46conversion. 47 48The additions since 0.89 include the ability to read from a PNG stream 49which has had some (or all) of the signature bytes read by the calling 50application. This also allows the reading of embedded PNG streams that 51do not have the PNG file signature. As well, it is now possible to set 52the library action on the detection of chunk CRC errors. It is possible 53to set different actions based on whether the CRC error occurred in a 54critical or an ancillary chunk. 55 56The changes made to the library, and bugs fixed are based on discussions 57on the PNG-implement mailing list and not on material submitted 58privately to Guy, Andreas, or Glenn. They will forward any good 59suggestions to the list. 60 61For a detailed description on using libpng, read libpng-manual.txt. For 62examples of libpng in a program, see example.c and pngtest.c. For usage 63information and restrictions (what little they are) on libpng, see 64png.h. For a description on using zlib (the compression library used by 65libpng) and zlib's restrictions, see zlib.h 66 67I have included a general makefile, as well as several machine and 68compiler specific ones, but you may have to modify one for your own needs. 69 70You should use zlib 1.0.4 or later to run this, but it MAY work with 71versions as old as zlib 0.95. Even so, there are bugs in older zlib 72versions which can cause the output of invalid compression streams for 73some images. You will definitely need zlib 1.0.4 or later if you are 74taking advantage of the MS-DOS "far" structure allocation for the small 75and medium memory models. You should also note that zlib is a 76compression library that is useful for more things than just PNG files. 77You can use zlib as a drop-in replacement for fread() and fwrite() if 78you are so inclined. 79 80zlib should be available at the same place that libpng is, or at. 81ftp://ftp.info-zip.org/pub/infozip/zlib 82 83You may also want a copy of the PNG specification. It is available 84as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find 85these at http://www.libpng.org/pub/png/documents/ 86 87This code is currently being archived at libpng.sf.net in the 88[DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT) 89at GO GRAPHSUP. If you can't find it in any of those places, 90e-mail me, and I'll help you find it. 91 92If you have any code changes, requests, problems, etc., please e-mail 93them to me. Also, I'd appreciate any make files or project files, 94and any modifications you needed to make to get libpng to compile, 95along with a #define variable to tell what compiler/system you are on. 96If you needed to add transformations to libpng, or wish libpng would 97provide the image in a different way, drop me a note (and code, if 98possible), so I can consider supporting the transformation. 99Finally, if you get any warning messages when compiling libpng 100(note: not zlib), and they are easy to fix, I'd appreciate the 101fix. Please mention "libpng" somewhere in the subject line. Thanks. 102 103This release was created and will be supported by myself (of course 104based in a large way on Guy's and Andreas' earlier work), and the PNG 105development group. 106 107Send comments/corrections/commendations to png-mng-implement at 108lists.sourceforge.net (subscription required; visit 109https://lists.sourceforge.net/lists/listinfo/png-mng-implement 110to subscribe) or to glennrp at users.sourceforge.net 111 112You can't reach Guy, the original libpng author, at the addresses 113given in previous versions of this document. He and Andreas will 114read mail addressed to the png-implement list, however. 115 116Please do not send general questions about PNG. Send them to 117png-mng-misc at lists.sf.net (subscription required; visit 118https://lists.sourceforge.net/lists/listinfo/png-mng-misc to 119subscribe). If you have a question about something 120in the PNG specification that is related to using libpng, send it 121to me. Send me any questions that start with "I was using libpng, 122and ...". If in doubt, send questions to me. I'll bounce them 123to others, if necessary. 124 125Please do not send suggestions on how to change PNG. We have 126been discussing PNG for sixteen years now, and it is official and 127finished. If you have suggestions for libpng, however, I'll 128gladly listen. Even if your suggestion is not used immediately, 129it may be used later. 130 131Files in this distribution: 132 133 ANNOUNCE => Announcement of this version, with recent changes 134 CHANGES => Description of changes between libpng versions 135 KNOWNBUG => List of known bugs and deficiencies 136 LICENSE => License to use and redistribute libpng 137 README => This file 138 TODO => Things not implemented in the current library 139 Y2KINFO => Statement of Y2K compliance 140 example.c => Example code for using libpng functions 141 libpng.3 => manual page for libpng (includes libpng-manual.txt) 142 libpng-manual.txt => Description of libpng and its functions 143 libpngpf.3 => manual page for libpng's private functions 144 png.5 => manual page for the PNG format 145 png.c => Basic interface functions common to library 146 png.h => Library function and interface declarations (public) 147 pngpriv.h => Library function and interface declarations (private) 148 pngconf.h => System specific library configuration (public) 149 pngstruct.h => png_struct declaration (private) 150 pnginfo.h => png_info struct declaration (private) 151 pngdebug.h => debugging macros (private) 152 pngerror.c => Error/warning message I/O functions 153 pngget.c => Functions for retrieving info from struct 154 pngmem.c => Memory handling functions 155 pngbar.png => PNG logo, 88x31 156 pngnow.png => PNG logo, 98x31 157 pngpread.c => Progressive reading functions 158 pngread.c => Read data/helper high-level functions 159 pngrio.c => Lowest-level data read I/O functions 160 pngrtran.c => Read data transformation functions 161 pngrutil.c => Read data utility functions 162 pngset.c => Functions for storing data into the info_struct 163 pngtest.c => Library test program 164 pngtest.png => Library test sample image 165 pngtrans.c => Common data transformation functions 166 pngwio.c => Lowest-level write I/O functions 167 pngwrite.c => High-level write functions 168 pngwtran.c => Write data transformations 169 pngwutil.c => Write utility functions 170 contrib => Contributions 171 gregbook => source code for PNG reading and writing, from 172 Greg Roelofs' "PNG: The Definitive Guide", 173 O'Reilly, 1999 174 msvctest => Builds and runs pngtest using a MSVC workspace 175 pngminus => Simple pnm2png and png2pnm programs 176 pngsuite => Test images 177 visupng => Contains a MSVC workspace for VisualPng 178 projects => Contains project files and workspaces for 179 building a DLL 180 cbuilder5 => Contains a Borland workspace for building 181 libpng and zlib 182 visualc6 => Contains a Microsoft Visual C++ (MSVC) 183 workspace for building libpng and zlib 184 visualc71 => Contains a Microsoft Visual C++ (MSVC) 185 workspace for building libpng and zlib 186 xcode => Contains an Apple xcode 187 workspace for building libpng and zlib 188 scripts => Directory containing scripts for building libpng: 189 (see scripts/README.txt for the list of scripts) 190 191Good luck, and happy coding. 192 193-Glenn Randers-Pehrson (current maintainer, since 1998) 194 Internet: glennrp at users.sourceforge.net 195 196-Andreas Eric Dilger (former maintainer, 1996-1997) 197 Internet: adilger at enel.ucalgary.ca 198 Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/ 199 200-Guy Eric Schalnat (original author and former maintainer, 1995-1996) 201 (formerly of Group 42, Inc) 202 Internet: gschal at infinet.com 203
