src/png/README

   1 README for libpng version 1.2.20 - September 8, 2007 (shared library 12.0)
   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
   7 or libpng-*.tar.bz2 if you want UNIX-style line endings in the text
   8 files, 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
  58 and not on material submitted privately to Guy, Andreas, or Glenn.  They will
  59 forward any good suggestions to the list.
  60
  61 For a detailed description on using libpng, read libpng.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.
  81 ftp://ftp.info-zip.org/pub/infozip/zlib
  82
  83 You may also want a copy of the PNG specification.  It is available
  84 as an RFC, a W3C Recommendation, and an ISO/IEC Standard.  You can find
  85 these at http://www.libpng.org/pub/png/documents/
  86
  87 This code is currently being archived at libpng.sf.net in the
  88 [DOWNLOAD] area, and on CompuServe, Lib 20 (PNG SUPPORT)
  89 at GO GRAPHSUP.  If you can't find it in any of those places,
  90 e-mail me, and I'll help you find it.
  91
  92 If you have any code changes, requests, problems, etc., please e-mail
  93 them to me.  Also, I'd appreciate any make files or project files,
  94 and any modifications you needed to make to get libpng to compile,
  95 along with a #define variable to tell what compiler/system you are on.
  96 If you needed to add transformations to libpng, or wish libpng would
  97 provide the image in a different way, drop me a note (and code, if
  98 possible), so I can consider supporting the transformation.
  99 Finally, if you get any warning messages when compiling libpng
 100 (note: not zlib), and they are easy to fix, I'd appreciate the
 101 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
 102
 103 This release was created and will be supported by myself (of course
 104 based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 105
 106 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 107 (subscription required; visit
 108 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
 109 to subscribe) or to glennrp at users.sourceforge.net
 110
 111 You can't reach Guy, the original libpng author, at the addresses
 112 given in previous versions of this document.  He and Andreas will read mail
 113 addressed to the png-implement list, however.
 114
 115 Please do not send general questions about PNG.  Send them to
 116 the (png-list at ccrc.wustl.edu, subscription required, write to
 117 majordomo at ccrc.wustl.edu with "subscribe png-list" in your message).
 118 On the other hand,
 119 please do not send libpng questions to that address, send them to me
 120 or to the png-implement list.  I'll
 121 get them in the end anyway.  If you have a question about something
 122 in the PNG specification that is related to using libpng, send it
 123 to me.  Send me any questions that start with "I was using libpng,
 124 and ...".  If in doubt, send questions to me.  I'll bounce them
 125 to others, if necessary.
 126
 127 Please do not send suggestions on how to change PNG.  We have
 128 been discussing PNG for nine years now, and it is official and
 129 finished.  If you have suggestions for libpng, however, I'll
 130 gladly listen.  Even if your suggestion is not used immediately,
 131 it may be used later.
 132
 133 Files in this distribution:
 134
 135       ANNOUNCE      =>  Announcement of this version, with recent changes
 136       CHANGES       =>  Description of changes between libpng versions
 137       KNOWNBUG      =>  List of known bugs and deficiencies
 138       LICENSE       =>  License to use and redistribute libpng
 139       README        =>  This file
 140       TODO          =>  Things not implemented in the current library
 141       Y2KINFO       =>  Statement of Y2K compliance
 142       example.c     =>  Example code for using libpng functions
 143       libpng.3      =>  manual page for libpng (includes libpng.txt)
 144       libpng.txt    =>  Description of libpng and its functions
 145       libpngpf.3    =>  manual page for libpng's private functions
 146       png.5         =>  manual page for the PNG format
 147       png.c         =>  Basic interface functions common to library
 148       png.h         =>  Library function and interface declarations
 149       pngconf.h     =>  System specific library configuration
 150       pngasmrd.h    =>  Header file for assembler-coded functions
 151       pngerror.c    =>  Error/warning message I/O functions
 152       pngget.c      =>  Functions for retrieving info from struct
 153       pngmem.c      =>  Memory handling functions
 154       pngbar.png    =>  PNG logo, 88x31
 155       pngnow.png    =>  PNG logo, 98x31
 156       pngpread.c    =>  Progressive reading functions
 157       pngread.c     =>  Read data/helper high-level functions
 158       pngrio.c      =>  Lowest-level data read I/O functions
 159       pngrtran.c    =>  Read data transformation functions
 160       pngrutil.c    =>  Read data utility functions
 161       pngset.c      =>  Functions for storing data into the info_struct
 162       pngtest.c     =>  Library test program
 163       pngtest.png   =>  Library test sample image
 164       pngtrans.c    =>  Common data transformation functions
 165       pngwio.c      =>  Lowest-level write I/O functions
 166       pngwrite.c    =>  High-level write functions
 167       pngwtran.c    =>  Write data transformations
 168       pngwutil.c    =>  Write utility functions
 169       contrib       =>  Contributions
 170        gregbook         =>  source code for PNG reading and writing, from
 171                             Greg Roelofs' "PNG: The Definitive Guide",
 172                             O'Reilly, 1999
 173        msvctest     =>  Builds and runs pngtest using a MSVC workspace
 174        pngminus     =>  Simple pnm2png and png2pnm programs
 175        pngsuite     =>  Test images
 176        visupng      =>  Contains a MSVC workspace for VisualPng
 177       projects      =>  Contains project files and workspaces for building DLL
 178        beos             =>  Contains a Beos workspace for building libpng
 179        c5builder        =>  Contains a Borland workspace for building libpng
 180                             and zlib
 181        visualc6         =>  Contains a Microsoft Visual C++ (MSVC) workspace
 182                             for building libpng and zlib
 183        netware.txt      =>  Contains instructions for downloading a set of
 184                             project files for building libpng and zlib on
 185                             Netware.
 186        wince.txt        =>  Contains instructions for downloading a Microsoft
 187                             Visual C++ (Windows CD Toolkit) workspace for
 188                             building libpng and zlib on WindowsCE
 189       scripts       =>  Directory containing scripts for building libpng:
 190        descrip.mms      =>  VMS makefile for MMS or MMK
 191        makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)
 192        makefile.elf     =>  Linux/ELF makefile symbol versioning,
 193                             gcc, creates libpng12.so.0.1.2.20)
 194        makefile.linux   =>  Linux/ELF makefile
 195                             (gcc, creates libpng12.so.0.1.2.20)
 196        makefile.gcmmx   =>  Linux/ELF makefile
 197                             (gcc, creates libpng12.so.0.1.2.20,
 198                             uses assembler code tuned for Intel MMX platform)
 199        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
 200        makefile.knr     =>  Archaic UNIX Makefile that converts files with
 201                             ansi2knr (Requires ansi2knr.c from
 202                             ftp://ftp.cs.wisc.edu/ghost)
 203        makefile.aix     =>  AIX makefile
 204        makefile.cygwin  =>  Cygwin/gcc makefile
 205        makefile.darwin  =>  Darwin makefile
 206        makefile.dec     =>  DEC Alpha UNIX makefile
 207        makefile.freebsd =>  FreeBSD makefile
 208        makefile.hpgcc   =>  HPUX makefile using gcc
 209        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
 210        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
 211        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
 212        makefile.intel   =>  Intel C/C++ version 4.0 and later
 213        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
 214        makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.
 215        makefile.ne12bsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng12.so
 216        makefile.openbsd =>  OpenBSD makefile
 217        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
 218        makefile.sggcc   =>  Silicon Graphics
 219                             (gcc, creates libpng12.so.0.1.2.20)
 220        makefile.sunos   =>  Sun makefile
 221        makefile.solaris =>  Solaris 2.X makefile
 222                             (gcc, creates libpng12.so.0.1.2.20)
 223        makefile.so9     =>  Solaris 9 makefile
 224                             (gcc, creates libpng12.so.0.1.2.20)
 225        makefile.32sunu  =>  Sun Ultra 32-bit makefile
 226        makefile.64sunu  =>  Sun Ultra 64-bit makefile
 227        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 228        makefile.mips    =>  MIPS makefile
 229        makefile.acorn   =>  Acorn makefile
 230        makefile.amiga   =>  Amiga makefile
 231        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
 232                             compiler (Requires SCOPTIONS, copied from
 233                             scripts/SCOPTIONS.ppc)
 234        makefile.atari   =>  Atari makefile
 235        makefile.beos    =>  BEOS makefile for X86
 236        makefile.bor     =>  Borland makefile (uses bcc)
 237        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
 238        makefile.tc3     =>  Turbo C 3.0 makefile
 239        makefile.dj2     =>  DJGPP 2 makefile
 240        makefile.msc     =>  Microsoft C makefile
 241        makefile.vcawin32=>  makefile for Microsoft Visual C++ 5.0 and
 242                             later (uses assembler code tuned for Intel MMX
 243                             platform)
 244        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
 245                             later (does not use assembler code)
 246        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 247        pngos2.def       =>  OS/2 module definition file used by makefile.os2
 248        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 249        makevms.com      =>  VMS build script
 250        SCOPTIONS.ppc    =>  Used with smakefile.ppc
 251
 252 Good luck, and happy coding.
 253
 254 -Glenn Randers-Pehrson (current maintainer)
 255  Internet: glennrp at users.sourceforge.net
 256
 257 -Andreas Eric Dilger (former maintainer, 1996-1997)
 258  Internet: adilger at enel.ucalgary.ca
 259  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 260
 261 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
 262  (formerly of Group 42, Inc)
 263  Internet: gschal at infinet.com