1README for libpng version 1.2.46 - July 9, 2011 (shared library 12.0) 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 8endings in the text files, or lpng*.7z or lpng*.zip if you want DOS-style 9line endings. You can get UNIX-style line endings from the *.zip file 10by using "unzip -a" but there seems to be no simple way to recover 11UNIX-style line endings from the *.7z file. The *.tar.xz file is 12recommended for *NIX users instead. 13 14Version 0.89 was the first official release of libpng. Don't let the 15fact that it's the first release fool you. The libpng library has been in 16extensive use and testing since mid-1995. By late 1997 it had 17finally gotten to the stage where there hadn't been significant 18changes to the API in some time, and people have a bad feeling about 19libraries with versions < 1.0. Version 1.0.0 was released in 20March 1998. 21 22**** 23Note that some of the changes to the png_info structure render this 24version of the library binary incompatible with libpng-0.89 or 25earlier versions if you are using a shared library. The type of the 26"filler" parameter for png_set_filler() has changed from png_byte to 27png_uint_32, which will affect shared-library applications that use 28this function. 29 30To avoid problems with changes to the internals of png_info_struct, 31new APIs have been made available in 0.95 to avoid direct application 32access to info_ptr. These functions are the png_set_<chunk> and 33png_get_<chunk> functions. These functions should be used when 34accessing/storing the info_struct data, rather than manipulating it 35directly, to avoid such problems in the future. 36 37It is important to note that the APIs do not make current programs 38that access the info struct directly incompatible with the new 39library. However, it is strongly suggested that new programs use 40the new APIs (as shown in example.c and pngtest.c), and older programs 41be converted to the new format, to facilitate upgrades in the future. 42**** 43 44Additions since 0.90 include the ability to compile libpng as a 45Windows DLL, and new APIs for accessing data in the info struct. 46Experimental functions include the ability to set weighting and cost 47factors for row filter selection, direct reads of integers from buffers 48on big-endian processors that support misaligned data access, faster 49methods of doing alpha composition, and more accurate 16->8 bit color 50conversion. 51 52The additions since 0.89 include the ability to read from a PNG stream 53which has had some (or all) of the signature bytes read by the calling 54application. This also allows the reading of embedded PNG streams that 55do not have the PNG file signature. As well, it is now possible to set 56the library action on the detection of chunk CRC errors. It is possible 57to set different actions based on whether the CRC error occurred in a 58critical or an ancillary chunk. 59 60The changes made to the library, and bugs fixed are based on discussions 61on the png-mng-implement mailing list and not on material submitted 62privately to Guy, Andreas, or Glenn. They will forward any good 63suggestions to the list. 64 65For a detailed description on using libpng, read libpng.txt. For 66examples of libpng in a program, see example.c and pngtest.c. For usage 67information and restrictions (what little they are) on libpng, see 68png.h. For a description on using zlib (the compression library used by 69libpng) and zlib's restrictions, see zlib.h 70 71I have included a general makefile, as well as several machine and 72compiler specific ones, but you may have to modify one for your own needs. 73 74You should use zlib 1.0.4 or later to run this, but it MAY work with 75versions as old as zlib 0.95. Even so, there are bugs in older zlib 76versions which can cause the output of invalid compression streams for 77some images. You will definitely need zlib 1.0.4 or later if you are 78taking advantage of the MS-DOS "far" structure allocation for the small 79and medium memory models. You should also note that zlib is a 80compression library that is useful for more things than just PNG files. 81You can use zlib as a drop-in replacement for fread() and fwrite() if 82you are so inclined. 83 84zlib should be available at the same place that libpng is, or at 85ftp://ftp.simplesystems.org/pub/png/src/ 86 87You may also want a copy of the PNG specification. It is available 88as an RFC, a W3C Recommendation, and an ISO/IEC Standard. You can find 89these at http://www.libpng.org/pub/png/pngdocs.html 90 91This code is currently being archived at libpng.sf.net in the 92[DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT) 93at GO GRAPHSUP. If you can't find it in any of those places, 94e-mail me, and I'll help you find it. 95 96If you have any code changes, requests, problems, etc., please e-mail 97them to me. Also, I'd appreciate any make files or project files, 98and any modifications you needed to make to get libpng to compile, 99along with a #define variable to tell what compiler/system you are on. 100If you needed to add transformations to libpng, or wish libpng would 101provide the image in a different way, drop me a note (and code, if 102possible), so I can consider supporting the transformation. 103Finally, if you get any warning messages when compiling libpng 104(note: not zlib), and they are easy to fix, I'd appreciate the 105fix. Please mention "libpng" somewhere in the subject line. Thanks. 106 107This release was created and will be supported by myself (of course 108based in a large way on Guy's and Andreas' earlier work), and the PNG 109development group. 110 111Send comments/corrections/commendations to png-mng-implement at lists.sf.net 112(subscription required; visit 113https://lists.sourceforge.net/lists/listinfo/png-mng-implement 114to subscribe) or to glennrp at users.sourceforge.net 115 116You can't reach Guy, the original libpng author, at the addresses 117given in previous versions of this document. He and Andreas will 118read mail addressed to the png-mng-implement list, however. 119 120Please do not send general questions about PNG. Send them to 121the (png-mng-misc at lists.sourceforge.net, subscription required, visit 122https://lists.sourceforge.net/lists/listinfo/png-mng-misc to 123subscribe). On the other hand, please do not send libpng questions to 124that address, send them to me or to the png-mng-implement list. I'll 125get them in the end anyway. If you have a question about something 126in the PNG specification that is related to using libpng, send it 127to me. Send me any questions that start with "I was using libpng, 128and ...". If in doubt, send questions to me. I'll bounce them 129to others, if necessary. 130 131Please do not send suggestions on how to change PNG. We have 132been discussing PNG for twelve years now, and it is official and 133finished. If you have suggestions for libpng, however, I'll 134gladly listen. Even if your suggestion is not used immediately, 135it may be used later. 136 137Files in this distribution: 138 139 ANNOUNCE => Announcement of this version, with recent changes 140 CHANGES => Description of changes between libpng versions 141 KNOWNBUG => List of known bugs and deficiencies 142 LICENSE => License to use and redistribute libpng 143 README => This file 144 TODO => Things not implemented in the current library 145 Y2KINFO => Statement of Y2K compliance 146 example.c => Example code for using libpng functions 147 libpng-*-*-diff.txt => Diff from previous release 148 libpng.3 => manual page for libpng (includes libpng.txt) 149 libpng.txt => Description of libpng and its functions 150 libpngpf.3 => manual page for libpng's private functions 151 png.5 => manual page for the PNG format 152 png.c => Basic interface functions common to library 153 png.h => Library function and interface declarations 154 pngconf.h => System specific library configuration 155 pngerror.c => Error/warning message I/O functions 156 pngget.c => Functions for retrieving info from struct 157 pngmem.c => Memory handling functions 158 pngbar.png => PNG logo, 88x31 159 pngnow.png => PNG logo, 98x31 160 pngpread.c => Progressive reading functions 161 pngread.c => Read data/helper high-level functions 162 pngrio.c => Lowest-level data read I/O functions 163 pngrtran.c => Read data transformation functions 164 pngrutil.c => Read data utility functions 165 pngset.c => Functions for storing data into the info_struct 166 pngtest.c => Library test program 167 pngtest.png => Library test sample image 168 pngtrans.c => Common data transformation functions 169 pngwio.c => Lowest-level write I/O functions 170 pngwrite.c => High-level write functions 171 pngwtran.c => Write data transformations 172 pngwutil.c => Write utility functions 173 contrib => Contributions 174 gregbook => source code for PNG reading and writing, from 175 Greg Roelofs' "PNG: The Definitive Guide", 176 O'Reilly, 1999 177 msvctest => Builds and runs pngtest using a MSVC workspace 178 pngminim => Simple pnm2pngm and png2pnmm programs 179 pngminus => Simple pnm2png and png2pnm programs 180 pngsuite => Test images 181 visupng => Contains a MSVC workspace for VisualPng 182 projects => Contains project files and workspaces for 183 building a DLL 184 beos => Contains a Beos workspace for building libpng 185 c5builder => Contains a Borland workspace for building 186 libpng and zlib 187 netware.txt => Contains instructions for downloading a set 188 of project files for building libpng and 189 zlib on Netware. 190 visualc6 => Contains a Microsoft Visual C++ (MSVC) 191 workspace for building libpng and zlib 192 wince.txt => Contains instructions for downloading a 193 Microsoft Visual C++ (Windows CD Toolkit) 194 workspace for building libpng and zlib on 195 WindowsCE 196 xcode => Contains xcode project files 197 scripts => Directory containing scripts for building libpng: 198 descrip.mms => VMS makefile for MMS or MMK 199 makefile.std => Generic UNIX makefile (cc, creates static 200 libpng.a) 201 makefile.elf => Linux/ELF gcc makefile symbol versioning, 202 creates libpng12.so.0.1.2.46) 203 makefile.linux => Linux/ELF makefile (gcc, creates 204 libpng12.so.0.1.2.46) 205 makefile.gcmmx => Linux/ELF makefile (gcc, creates 206 libpng12.so.0.1.2.46, previously 207 used assembler code tuned for Intel MMX 208 platform) 209 makefile.gcc => Generic makefile (gcc, creates static 210 libpng.a) 211 makefile.knr => Archaic UNIX Makefile that converts files 212 with ansi2knr (Requires ansi2knr.c from 213 ftp://ftp.cs.wisc.edu/ghost) 214 makefile.aix => AIX makefile 215 makefile.cygwin => Cygwin/gcc makefile 216 makefile.darwin => Darwin makefile 217 makefile.dec => DEC Alpha UNIX makefile 218 makefile.freebsd => FreeBSD makefile 219 makefile.hpgcc => HPUX makefile using gcc 220 makefile.hpux => HPUX (10.20 and 11.00) makefile 221 makefile.hp64 => HPUX (10.20 and 11.00) makefile, 64 bit 222 makefile.ibmc => IBM C/C++ version 3.x for Win32 and OS/2 223 (static) 224 makefile.intel => Intel C/C++ version 4.0 and later 225 libpng.icc => Project file, IBM VisualAge/C++ 4.0 or later 226 makefile.netbsd => NetBSD/cc makefile, makes libpng.so. 227 makefile.ne12bsd => NetBSD/cc makefile, makes libpng12.so 228 makefile.openbsd => OpenBSD makefile 229 makefile.sgi => Silicon Graphics IRIX (cc, creates static lib) 230 makefile.sggcc => Silicon Graphics 231 (gcc, creates libpng12.so.0.1.2.46) 232 makefile.sunos => Sun makefile 233 makefile.solaris => Solaris 2.X makefile 234 (gcc, creates libpng12.so.0.1.2.46) 235 makefile.so9 => Solaris 9 makefile 236 (gcc, creates libpng12.so.0.1.2.46) 237 makefile.32sunu => Sun Ultra 32-bit makefile 238 makefile.64sunu => Sun Ultra 64-bit makefile 239 makefile.sco => For SCO OSr5 ELF and Unixware 7 with Native cc 240 makefile.mips => MIPS makefile 241 makefile.acorn => Acorn makefile 242 makefile.amiga => Amiga makefile 243 smakefile.ppc => AMIGA smakefile for SAS C V6.58/7.00 PPC 244 compiler (Requires SCOPTIONS, copied from 245 scripts/SCOPTIONS.ppc) 246 makefile.atari => Atari makefile 247 makefile.beos => BEOS makefile for X86 248 makefile.bor => Borland makefile (uses bcc) 249 makefile.bc32 => 32-bit Borland C++ (all modules compiled in C mode) 250 makefile.tc3 => Turbo C 3.0 makefile 251 makefile.dj2 => DJGPP 2 makefile 252 makefile.msc => Microsoft C makefile 253 makefile.vcawin32=> makefile for Microsoft Visual C++ 5.0 and 254 later (previously used assembler code tuned 255 for Intel MMX platform) 256 makefile.vcwin32 => makefile for Microsoft Visual C++ 4.0 and 257 later (does not use assembler code) 258 makefile.os2 => OS/2 Makefile (gcc and emx, requires pngos2.def) 259 pngos2.def => OS/2 module definition file used by makefile.os2 260 makefile.watcom => Watcom 10a+ Makefile, 32-bit flat memory model 261 makevms.com => VMS build script 262 SCOPTIONS.ppc => Used with smakefile.ppc 263 264Good luck, and happy coding. 265 266-Glenn Randers-Pehrson (current maintainer, since 1998) 267 Internet: glennrp at users.sourceforge.net 268 269-Andreas Eric Dilger (former maintainer, 1996-1997) 270 Internet: adilger at enel.ucalgary.ca 271 Web: http://members.shaw.ca/adilger/ 272 273-Guy Eric Schalnat (original author and former maintainer, 1995-1996) 274 (formerly of Group 42, Inc) 275 Internet: gschal at infinet.com 276
