src/png/README

   1 README for libpng version 1.4.4 - September 23, 2010 (shared library 14.0)
   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 libpng-*.tar.xz or libpng-*.tar.bz2 if you want UNIX-style line endings
   8 in the text 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 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.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
 105 development group.
 106
 107 Send comments/corrections/commendations to png-mng-implement at
 108 lists.sourceforge.net (subscription required; visit
 109 https://lists.sourceforge.net/lists/listinfo/png-mng-implement
 110 to subscribe) or to glennrp at users.sourceforge.net
 111
 112 You can't reach Guy, the original libpng author, at the addresses
 113 given in previous versions of this document.  He and Andreas will
 114 read mail addressed to the png-implement list, however.
 115
 116 Please do not send general questions about PNG.  Send them to
 117 the (png-list at ccrc.wustl.edu, subscription required, write to
 118 majordomo at ccrc.wustl.edu with "subscribe png-list" in your message).
 119 On the other hand,
 120 please do not send libpng questions to that address, send them to me
 121 or to the png-implement list.  I'll
 122 get them in the end anyway.  If you have a question about something
 123 in the PNG specification that is related to using libpng, send it
 124 to me.  Send me any questions that start with "I was using libpng,
 125 and ...".  If in doubt, send questions to me.  I'll bounce them
 126 to others, if necessary.
 127
 128 Please do not send suggestions on how to change PNG.  We have
 129 been discussing PNG for nine years now, and it is official and
 130 finished.  If you have suggestions for libpng, however, I'll
 131 gladly listen.  Even if your suggestion is not used immediately,
 132 it may be used later.
 133
 134 Files in this distribution:
 135
 136       ANNOUNCE      =>  Announcement of this version, with recent changes
 137       CHANGES       =>  Description of changes between libpng versions
 138       KNOWNBUG      =>  List of known bugs and deficiencies
 139       LICENSE       =>  License to use and redistribute libpng
 140       README        =>  This file
 141       TODO          =>  Things not implemented in the current library
 142       Y2KINFO       =>  Statement of Y2K compliance
 143       example.c     =>  Example code for using libpng functions
 144       libpng.3      =>  manual page for libpng (includes libpng.txt)
 145       libpng.txt    =>  Description of libpng and its functions
 146       libpngpf.3    =>  manual page for libpng's private functions
 147       png.5         =>  manual page for the PNG format
 148       png.c         =>  Basic interface functions common to library
 149       png.h         =>  Library function and interface declarations
 150       pngconf.h     =>  System specific library configuration
 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
 178                         building a DLL
 179        c5builder        =>  Contains a Borland workspace for building
 180                             libpng and zlib
 181        visualc6         =>  Contains a Microsoft Visual C++ (MSVC)
 182                             workspace for building libpng and zlib
 183       scripts       =>  Directory containing scripts for building libpng:
 184        descrip.mms      =>  VMS makefile for MMS or MMK
 185        makefile.std     =>  Generic UNIX makefile (cc, creates static
 186                             libpng.a)
 187        makefile.elf     =>  Linux/ELF makefile symbol versioning,
 188                             (gcc, creates libpng14.so.14.1.4.4)
 189        makefile.linux   =>  Linux/ELF makefile
 190                             (gcc, creates libpng14.so.14.1.4.4)
 191        makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)
 192        makefile.knr     =>  Archaic UNIX Makefile that converts files with
 193                             ansi2knr (Requires ansi2knr.c from
 194                             ftp://ftp.cs.wisc.edu/ghost)
 195        makefile.aix     =>  AIX makefile
 196        makefile.cygwin  =>  Cygwin/gcc makefile
 197        makefile.darwin  =>  Darwin makefile
 198        makefile.dec     =>  DEC Alpha UNIX makefile
 199        makefile.freebsd =>  FreeBSD makefile
 200        makefile.hpgcc   =>  HPUX makefile using gcc
 201        makefile.hpux    =>  HPUX (10.20 and 11.00) makefile
 202        makefile.hp64    =>  HPUX (10.20 and 11.00) makefile, 64 bit
 203        makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)
 204        makefile.intel   =>  Intel C/C++ version 4.0 and later
 205        makefile.mingw   =>  Mingw/gcc makefile
 206        makefile.netbsd  =>  NetBSD/cc makefile, makes libpng.so.
 207        makefile.ne14bsd  =>  NetBSD/cc makefile, makes
 208                             libpng14.so
 209        makefile.openbsd =>  OpenBSD makefile
 210        makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)
 211        makefile.sggcc   =>  Silicon Graphics
 212                             (gcc, creates libpng14.so.14.1.4.4)
 213        makefile.sunos   =>  Sun makefile
 214        makefile.solaris =>  Solaris 2.X makefile
 215                             (gcc, creates libpng14.so.14.1.4.4)
 216        makefile.so9     =>  Solaris 9 makefile
 217                             (gcc, creates libpng14.so.14.1.4.4)
 218        makefile.32sunu  =>  Sun Ultra 32-bit makefile
 219        makefile.64sunu  =>  Sun Ultra 64-bit makefile
 220        makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc
 221        makefile.mips    =>  MIPS makefile
 222        makefile.acorn   =>  Acorn makefile
 223        makefile.amiga   =>  Amiga makefile
 224        smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC
 225                             compiler (Requires SCOPTIONS, copied from
 226                             scripts/SCOPTIONS.ppc)
 227        makefile.atari   =>  Atari makefile
 228        makefile.beos    =>  BEOS makefile for X86
 229        makefile.bor     =>  Borland makefile (uses bcc)
 230        makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)
 231        makefile.tc3     =>  Turbo C 3.0 makefile
 232        makefile.dj2     =>  DJGPP 2 makefile
 233        makefile.msc     =>  Microsoft C makefile
 234        makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and
 235                             later (does not use assembler code)
 236        makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 237        png32ce.def      =>  module definition for makefile.cegccg
 238        pngos2.def       =>  OS/2 module definition file used by
 239                             makefile.os2
 240        pngwin.def       =>  module definition file used by
 241                             makefile.cygwin and makefile.mingw
 242        makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 243        makevms.com      =>  VMS build script
 244        SCOPTIONS.ppc    =>  Used with smakefile.ppc
 245
 246 Good luck, and happy coding.
 247
 248 -Glenn Randers-Pehrson (current maintainer, since 1998)
 249  Internet: glennrp at users.sourceforge.net
 250
 251 -Andreas Eric Dilger (former maintainer, 1996-1997)
 252  Internet: adilger at enel.ucalgary.ca
 253  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 254
 255 -Guy Eric Schalnat (original author and former maintainer, 1995-1996)
 256  (formerly of Group 42, Inc)
 257  Internet: gschal at infinet.com