1 README for libpng version 1.6.10 - March 6, 2014 (shared library 16.0) 2 See the note about version numbers near the top of png.h 3 4 See INSTALL for instructions on how to install libpng. 5 6 Libpng comes in several distribution formats. Get libpng-*.tar.gz or 7 libpng-*.tar.xz or if you want UNIX-style line endings in the text files, 8 or lpng*.7z or lpng*.zip if you want DOS-style line endings. 9 10 Version 0.89 was the first official release of libpng. Don't let the 11 fact that it's the first release fool you. The libpng library has been in 12 extensive use and testing since mid-1995. By late 1997 it had 13 finally gotten to the stage where there hadn't been significant 14 changes to the API in some time, and people have a bad feeling about 15 libraries with versions < 1.0. Version 1.0.0 was released in 16 March 1998. 17 18 **** 19 Note that some of the changes to the png_info structure render this 20 version of the library binary incompatible with libpng-0.89 or 21 earlier 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 23 png_uint_32, which will affect shared-library applications that use 24 this function. 25 26 To avoid problems with changes to the internals of png_info_struct, 27 new APIs have been made available in 0.95 to avoid direct application 28 access to info_ptr. These functions are the png_set_<chunk> and 29 png_get_<chunk> functions. These functions should be used when 30 accessing/storing the info_struct data, rather than manipulating it 31 directly, to avoid such problems in the future. 32 33 It is important to note that the APIs do not make current programs 34 that access the info struct directly incompatible with the new 35 library. However, it is strongly suggested that new programs use 36 the new APIs (as shown in example.c and pngtest.c), and older programs 37 be converted to the new format, to facilitate upgrades in the future. 38 **** 39 40 Additions since 0.90 include the ability to compile libpng as a 41 Windows DLL, and new APIs for accessing data in the info struct. 42 Experimental functions include the ability to set weighting and cost 43 factors for row filter selection, direct reads of integers from buffers 44 on big-endian processors that support misaligned data access, faster 45 methods of doing alpha composition, and more accurate 16->8 bit color 46 conversion. 47 48 The additions since 0.89 include the ability to read from a PNG stream 49 which has had some (or all) of the signature bytes read by the calling 50 application. This also allows the reading of embedded PNG streams that 51 do not have the PNG file signature. As well, it is now possible to set 52 the library action on the detection of chunk CRC errors. It is possible 53 to set different actions based on whether the CRC error occurred in a 54 critical or an ancillary chunk. 55 56 The changes made to the library, and bugs fixed are based on discussions 57 on the PNG-implement mailing list and not on material submitted 58 privately to Guy, Andreas, or Glenn. They will forward any good 59 suggestions to the list. 60 61 For a detailed description on using libpng, read libpng-manual.txt. For 62 examples of libpng in a program, see example.c and pngtest.c. For usage 63 information and restrictions (what little they are) on libpng, see 64 png.h. For a description on using zlib (the compression library used by 65 libpng) and zlib's restrictions, see zlib.h 66 67 I have included a general makefile, as well as several machine and 68 compiler specific ones, but you may have to modify one for your own needs. 69 70 You should use zlib 1.0.4 or later to run this, but it MAY work with 71 versions as old as zlib 0.95. Even so, there are bugs in older zlib 72 versions which can cause the output of invalid compression streams for 73 some images. You will definitely need zlib 1.0.4 or later if you are 74 taking advantage of the MS-DOS "far" structure allocation for the small 75 and medium memory models. You should also note that zlib is a 76 compression library that is useful for more things than just PNG files. 77 You can use zlib as a drop-in replacement for fread() and fwrite() if 78 you are so inclined. 79 80 zlib should be available at the same place that libpng is, or at zlib.net. 81 82 You may also want a copy of the PNG specification. It is available 83 as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find 84 these at http://www.libpng.org/pub/png/documents/ 85 86 This code is currently being archived at libpng.sf.net in the 87 [DOWNLOAD] area, and at ftp://ftp.simplesystems.org. If you can't find it 88 in any of those places, e-mail me, and I'll help you find it. 89 90 If you have any code changes, requests, problems, etc., please e-mail 91 them to me. Also, I'd appreciate any make files or project files, 92 and any modifications you needed to make to get libpng to compile, 93 along with a #define variable to tell what compiler/system you are on. 94 If you needed to add transformations to libpng, or wish libpng would 95 provide the image in a different way, drop me a note (and code, if 96 possible), so I can consider supporting the transformation. 97 Finally, if you get any warning messages when compiling libpng 98 (note: not zlib), and they are easy to fix, I'd appreciate the 99 fix. Please mention "libpng" somewhere in the subject line. Thanks. 100 101 This release was created and will be supported by myself (of course 102 based in a large way on Guy's and Andreas' earlier work), and the PNG 103 development group. 104 105 Send comments/corrections/commendations to png-mng-implement at 106 lists.sourceforge.net (subscription required; visit 107 https://lists.sourceforge.net/lists/listinfo/png-mng-implement 108 to subscribe) or to glennrp at users.sourceforge.net 109 110 You can't reach Guy, the original libpng author, at the addresses 111 given in previous versions of this document. He and Andreas will 112 read mail addressed to the png-implement list, however. 113 114 Please do not send general questions about PNG. Send them to 115 png-mng-misc at lists.sf.net (subscription required; visit 116 https://lists.sourceforge.net/lists/listinfo/png-mng-misc to 117 subscribe). If you have a question about something 118 in the PNG specification that is related to using libpng, send it 119 to me. Send me any questions that start with "I was using libpng, 120 and ...". If in doubt, send questions to me. I'll bounce them 121 to others, if necessary. 122 123 Please do not send suggestions on how to change PNG. We have 124 been discussing PNG for nineteen years now, and it is official and 125 finished. If you have suggestions for libpng, however, I'll 126 gladly listen. Even if your suggestion is not used immediately, 127 it may be used later. 128 129 Files in this distribution: 130 131 ANNOUNCE => Announcement of this version, with recent changes 132 CHANGES => Description of changes between libpng versions 133 KNOWNBUG => List of known bugs and deficiencies 134 LICENSE => License to use and redistribute libpng 135 README => This file 136 TODO => Things not implemented in the current library 137 Y2KINFO => Statement of Y2K compliance 138 example.c => Example code for using libpng functions 139 libpng.3 => manual page for libpng (includes libpng-manual.txt) 140 libpng-manual.txt => Description of libpng and its functions 141 libpngpf.3 => manual page for libpng's private functions 142 png.5 => manual page for the PNG format 143 png.c => Basic interface functions common to library 144 png.h => Library function and interface declarations (public) 145 pngpriv.h => Library function and interface declarations (private) 146 pngconf.h => System specific library configuration (public) 147 pngstruct.h => png_struct declaration (private) 148 pnginfo.h => png_info struct declaration (private) 149 pngdebug.h => debugging macros (private) 150 pngerror.c => Error/warning message I/O functions 151 pngget.c => Functions for retrieving info from struct 152 pngmem.c => Memory handling functions 153 pngbar.png => PNG logo, 88x31 154 pngnow.png => PNG logo, 98x31 155 pngpread.c => Progressive reading functions 156 pngread.c => Read data/helper high-level functions 157 pngrio.c => Lowest-level data read I/O functions 158 pngrtran.c => Read data transformation functions 159 pngrutil.c => Read data utility functions 160 pngset.c => Functions for storing data into the info_struct 161 pngtest.c => Library test program 162 pngtest.png => Library test sample image 163 pngtrans.c => Common data transformation functions 164 pngwio.c => Lowest-level write I/O functions 165 pngwrite.c => High-level write functions 166 pngwtran.c => Write data transformations 167 pngwutil.c => Write utility functions 168 arm => Contains optimized code for the ARM platform 169 contrib => Contributions 170 examples => Example programs 171 gregbook => source code for PNG reading and writing, from 172 Greg Roelofs' "PNG: The Definitive Guide", 173 O'Reilly, 1999 174 libtests => Test programs 175 pngminim => Minimal decoder, encoder, and progressive decoder 176 programs demonstrating use of pngusr.dfa 177 pngminus => Simple pnm2png and png2pnm programs 178 pngsuite => Test images 179 tools => Various tools 180 visupng => Contains a MSVC workspace for VisualPng 181 projects => Contains project files and workspaces for 182 building a DLL 183 owatcom => Contains a WATCOM project for building libpng 184 visualc71 => Contains a Microsoft Visual C++ (MSVC) 185 workspace for building libpng and zlib 186 vstudio => Contains a Microsoft Visual C++ (MSVC) 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) 190 191 Good 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
