src/png/README

   1 README for libpng version 1.2.6 - August 15, 2004 (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 implementation mailing list <png-implement@ccrc.wustl.edu>
  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.
  81 If not, it should be at ftp.uu.net in /graphics/png
  82 Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib
  83
  84 You may also want a copy of the PNG specification.  It is available
  85 as an RFC and a W3C Recommendation.  Failing
  86 these resources you can try ftp.uu.net in the /graphics/png directory.
  87
  88 This code is currently being archived at ftp.uu.net in the
  89 /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
  90 at GO GRAPHSUP.  If you can't find it in any of those places,
  91 e-mail me, and I'll help you find it.
  92
  93 If you have any code changes, requests, problems, etc., please e-mail
  94 them to me.  Also, I'd appreciate any make files or project files,
  95 and any modifications you needed to make to get libpng to compile,
  96 along with a #define variable to tell what compiler/system you are on.
  97 If you needed to add transformations to libpng, or wish libpng would
  98 provide the image in a different way, drop me a note (and code, if
  99 possible), so I can consider supporting the transformation.
 100 Finally, if you get any warning messages when compiling libpng
 101 (note: not zlib), and they are easy to fix, I'd appreciate the
 102 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
 103
 104 This release was created and will be supported by myself (of course
 105 based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 106
 107 glennrp@users.sourceforge.net
 108 png-implement@ccrc.wustl.edu
 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 read mail
 112 addressed to the png-implement list, however.
 113
 114 Please do not send general questions about PNG.  Send them to
 115 the address in the specification (png-group@w3.org).  At the same
 116 time, please do not send libpng questions to that address, send them to me
 117 or to png-implement@ccrc.wustl.edu.  I'll
 118 get them in the end anyway.  If you have a question about something
 119 in the PNG specification that is related to using libpng, send it
 120 to me.  Send me any questions that start with "I was using libpng,
 121 and ...".  If in doubt, send questions to me.  I'll bounce them
 122 to others, if necessary.
 123
 124 Please do not send suggestions on how to change PNG.  We have
 125 been discussing PNG for three years now, and it is official and
 126 finished.  If you have suggestions for libpng, however, I'll
 127 gladly listen.  Even if your suggestion is not used for version
 128 1.0, it may be used later.
 129
 130 Files in this distribution:
 131
 132       ANNOUNCE      =>  Announcement of this version, with recent changes
 133       CHANGES       =>  Description of changes between libpng versions
 134       KNOWNBUG      =>  List of known bugs and deficiencies
 135       LICENSE       =>  License to use and redistribute libpng
 136       README        =>  This file
 137       TODO          =>  Things not implemented in the current library
 138       Y2KINFO       =>  Statement of Y2K compliance
 139       example.c     =>  Example code for using libpng functions
 140       libpng.3      =>  manual page for libpng (includes libpng.txt)
 141       libpng.txt    =>  Description of libpng and its functions
 142       libpngpf.3    =>  manual page for libpng's private functions
 143       png.5         =>  manual page for the PNG format
 144       png.c         =>  Basic interface functions common to library
 145       png.h         =>  Library function and interface declarations
 146       pngconf.h     =>  System specific library configuration
 147       pngasmrd.h    =>  Header file for assembler-coded functions
 148       pngerror.c    =>  Error/warning message I/O functions
 149       pngget.c      =>  Functions for retrieving info from struct
 150       pngmem.c      =>  Memory handling functions
 151       pngbar.png    =>  PNG logo, 88x31
 152       pngnow.png    =>  PNG logo, 98x31
 153       pngpread.c    =>  Progressive reading functions
 154       pngread.c     =>  Read data/helper high-level functions
 155       pngrio.c      =>  Lowest-level data read I/O functions
 156       pngrtran.c    =>  Read data transformation functions
 157       pngrutil.c    =>  Read data utility functions
 158       pngset.c      =>  Functions for storing data into the info_struct
 159       pngtest.c     =>  Library test program
 160       pngtest.png   =>  Library test sample image
 161       pngtrans.c    =>  Common data transformation functions
 162       pngwio.c      =>  Lowest-level write I/O functions
 163       pngwrite.c    =>  High-level write functions
 164       pngwtran.c    =>  Write data transformations
 165       pngwutil.c    =>  Write utility functions
 166       contrib       =>  Contributions
 167        gregbook         =>  source code for PNG reading and writing, from
 168                             Greg Roelofs' "PNG: The Definitive Guide",
 169                             O'Reilly, 1999
 170        msvctest     =>  Builds and runs pngtest using a MSVC workspace
 171        pngminus     =>  Simple pnm2png and png2pnm programs
 172        pngsuite     =>  Test images
 173        visupng      =>  Contains a MSVC workspace for VisualPng
 174       projects      =>  Contains project files and workspaces for building DLL
 175        beos             =>  Contains a Beos workspace for building libpng
 176        borland          =>  Contains a Borland workspace for building libpng
 177                             and zlib
 178        msvc             =>  Contains a Microsoft Visual C++ (MSVC) workspace
 179                             for building libpng and zlib
 180        netware.txt      =>  Contains instructions for downloading a set of
 181                             project files for building libpng and zlib on
 182                             Netware.
 183        wince.txt        =>  Contains instructions for downloading a Microsoft
 184                             Visual C++ (Windows CD Toolkit) workspace for
 185                             building libpng and zlib on WindowsCE
 186       scripts       =>  Directory containing scripts for building libpng:
 187        descrip.mms      =>  VMS makefile for MMS or MMK
 188        makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)
 189        makefile.linux   =>  Linux/ELF makefile
 190                             (gcc, creates libpng12.so.0.1.2.5)
 191        makefile.gcmmx   =>  Linux/ELF makefile (gcc, creates
 192                             libpng12.so.0.1.2.5, uses assembler code
 193                             tuned for Intel MMX platform)
 194        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
 195        makefile.knr     =>  Archaic UNIX Makefile that converts files with
 196                             ansi2knr (Requires ansi2knr.c from
 197                             ftp://ftp.cs.wisc.edu/ghost)
 198        makefile.aix     =>  AIX makefile
 199        makefile.cygwin  =>  Cygwin/gcc makefile
 200        makefile.darwin  =>  Darwin makefile
 201        makefile.dec     =>  DEC Alpha UNIX makefile
 202        makefile.freebsd =>  FreeBSD makefile
 203        makefile.hpgcc   =>  HPUX makefile using gcc
 204        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
 205        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
 206        makefile.intel   =>  Intel C/C++ version 4.0 and later
 207        libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later
 208        makefile.macosx  =>  MACOS X Makefile
 209        makefile.netbsd  =>  NetBSD/cc makefile, PNGGCCRD, makes libpng.so.
 210        makefile.ne0bsd =>  NetBSD/cc makefile, PNGGCCRD, makes libpng0.so
 211        makefile.openbsd =>  OpenBSD makefile
 212        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
 213        makefile.sggcc   =>  Silicon Graphics (gcc, creates libpng12.so.0.1.2.5)
 214        makefile.sunos   =>  Sun makefile
 215        makefile.solaris =>  Solaris 2.X makefile
 216                             (gcc, creates libpng12.so.0.1.2.5)
 217        makefile.so9     =>  Solaris 9 makefile
 218                             (gcc, creates libpng12.so.0.1.2.5)
 219        makefile.32sunu  =>  Sun Ultra 32-bit makefile
 220        makefile.64sunu  =>  Sun Ultra 64-bit makefile
 221        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 222        makefile.mips    =>  MIPS makefile
 223        makefile.acorn   =>  Acorn makefile
 224        makefile.amiga   =>  Amiga makefile
 225        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
 226                             compiler (Requires SCOPTIONS, copied from
 227                             scripts/SCOPTIONS.ppc)
 228        makefile.atari   =>  Atari makefile
 229        makefile.beos    =>  BEOS makefile for X86
 230        makefile.bor     =>  Borland makefile (uses bcc)
 231        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
 232        makefile.bd32    =>  To make a png32bd.dll with Borland C++ 4.5
 233        makefile.tc3     =>  Turbo C 3.0 makefile
 234        makefile.dj2     =>  DJGPP 2 makefile
 235        makefile.msc     =>  Microsoft C makefile
 236        makefile.vcawin32 => makefile for Microsoft Visual C++ 5.0 and
 237                             later (uses assembler code tuned for Intel MMX
 238                             platform)
 239        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
 240                             later (does not use assembler code)
 241        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 242        pngos2.def       =>  OS/2 module definition file used by makefile.os2
 243        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 244        makevms.com      =>  VMS build script
 245        pngdef.pas       =>  Defines for a png32bd.dll with Borland C++ 4.5
 246        SCOPTIONS.ppc    =>  Used with smakefile.ppc
 247       mangle        =>  Directory containing scripts to build libpng12m.so:
 248        mangle.in        =>  Function-decoration macros added to png.h by the
 249                             makefiles.
 250        makefile.linux   =>  Linux/ELF makefile
 251                             (gcc, creates libpng12m.so.0.1.2.5)
 252        makefile.gcmmx   =>  Linux/ELF makefile (gcc, creates
 253                             libpng12.so.0m.1.2.5, uses assembler code
 254                             tuned for Intel MMX platform)
 255        makefile.sgi     =>  Silicon Graphics (cc, creates libpng12m.so)
 256        makefile.sggcc   =>  Silicon Graphics (gcc, creates libpng12m.so)
 257
 258 Good luck, and happy coding.
 259
 260 -Glenn Randers-Pehrson
 261  Internet: randeg@alum.rpi.edu
 262
 263 -Andreas Eric Dilger
 264  Internet: adilger@enel.ucalgary.ca
 265  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 266
 267 -Guy Eric Schalnat
 268  (formerly of Group 42, Inc)
 269  Internet: gschal@infinet.com