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| 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 |
