src/png/README

   1 README for libpng 1.0.1 (shared library 2.1)
   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 This is the first official release of libpng.  Don't let the fact that
   7 it's the first release fool you.  The libpng library has been in
   8 extensive use and testing for about two and a half years.  However, it's
   9 finally gotten to the stage where there haven't been significant
  10 changes to the API in some time, and people have a bad feeling about
  11 libraries with versions < 1.0.
  12
  13 ****
  14 Note that some of the changes to the png_info structure render this
  15 version of the library binary incompatible with libpng-0.89 or
  16 earlier versions if you are using a shared library.  The type of the
  17 "filler" parameter for png_set_filler() has changed from png_byte to
  18 png_uint_32, which will affect shared-library applications that use
  19 this function.
  20
  21 To avoid problems with changes to the internals of png_info_struct,
  22 new APIs have been made available in 0.95 to avoid direct application
  23 access to info_ptr.  These functions are the png_set_<chunk> and
  24 png_get_<chunk> functions.  These functions should be used when
  25 accessing/storing the info_struct data, rather than manipulating it
  26 directly, to avoid such problems in the future.
  27
  28 It is important to note that the APIs do not make current programs
  29 that access the info struct directly incompatible with the new
  30 library.  However, it is strongly suggested that new programs use
  31 the new APIs (as shown in example.c), and older programs be converted
  32 to the new format, to facilitate upgrades in the future.
  33 ****
  34
  35 Additions since 0.90 include the ability to compile libpng as a
  36 Windows DLL, and new APIs for accessing data in the info struct.
  37 Experimental functions include the ability to set weighting and cost
  38 factors for row filter selection, direct reads of integers from buffers
  39 on big-endian processors that support misaligned data access, faster
  40 methods of doing alpha composition, and more accurate 16->8 bit color
  41 conversion.
  42
  43 The additions since 0.89 include the ability to read from a PNG stream
  44 which has had some (or all) of the signature bytes read by the calling
  45 application.  This also allows the reading of embedded PNG streams that
  46 do not have the PNG file signature.  As well, it is now possible to set
  47 the library action on the detection of chunk CRC errors.  It is possible
  48 to set different actions based on whether the CRC error occurred in a
  49 critical or an ancillary chunk.
  50
  51 The changes made to the library, and bugs fixed are based on discussions
  52 on the PNG implementation mailing list <png-implement@dworking.wustl.edu>
  53 and not on material submitted to Guy.
  54
  55 For a detailed description on using libpng, read libpng.txt.  For
  56 examples of libpng in a program, see example.c and pngtest.c.  For usage
  57 information and restrictions (what little they are) on libpng, see
  58 png.h.  For a description on using zlib (the compression library used by
  59 libpng) and zlib's restrictions, see zlib.h
  60
  61 I have included a general makefile, as well as several machine and
  62 compiler specific ones, but you may have to modify one for your own needs.
  63
  64 You should use zlib 1.0.4 or later to run this, but it MAY work with
  65 versions as old as zlib 0.95.  Even so, there are bugs in older zlib
  66 versions which can cause the output of invalid compression streams for
  67 some images.  You will definitely need zlib 1.0.4 or later if you are
  68 taking advantage of the MS-DOS "far" structure allocation for the small
  69 and medium memory models.  You should also note that zlib is a
  70 compression library that is useful for more things than just PNG files.
  71 You can use zlib as a drop-in replacement for fread() and fwrite() if
  72 you are so inclined.
  73
  74 zlib should be available at the same place that libpng is.
  75 If not, it should be at ftp.uu.net in /graphics/png
  76 Eventually, it will be at ftp.uu.net in /pub/archiving/zip/zlib
  77
  78 You may also want a copy of the PNG specification.  It is available
  79 as an RFC and a W3C Recommendation.  Failing
  80 these resources you can try ftp.uu.net in the /graphics/png directory.
  81
  82 This code is currently being archived at ftp.uu.net in the
  83 /graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)
  84 at GO GRAPHSUP.  If you can't find it in any of those places,
  85 e-mail me, and I'll help you find it.
  86
  87 If you have any code changes, requests, problems, etc., please e-mail
  88 them to me.  Also, I'd appreciate any make files or project files,
  89 and any modifications you needed to make to get libpng to compile,
  90 along with a #define variable to tell what compiler/system you are on.
  91 If you needed to add transformations to libpng, or wish libpng would
  92 provide the image in a different way, drop me a note (and code, if
  93 possible), so I can consider supporting the transformation.
  94 Finally, if you get any warning messages when compiling libpng
  95 (note: not zlib), and they are easy to fix, I'd appreciate the
  96 fix.  Please mention "libpng" somewhere in the subject line.  Thanks.
  97
  98 This release was created and will be supported by myself (of course
  99 based in a large way on Guy's and Andreas' earlier work), and the PNG group.
 100
 101 randeg@alumni.rpi.edu
 102 png-implement@dworkin.wustl.edu
 103
 104 You can't reach Guy, the original libpng author, at the addresses
 105 given in previous versions of this document.  He and Andreas will read mail
 106 addressed to the png-implement list, however.
 107
 108 Please do not send general questions about PNG.  Send them to
 109 the address in the specification (png-group@w3.org).  At the same
 110 time, please do not send libpng questions to that address, send them to me
 111 or to png-implement@dworkin.wustl.edu.  I'll
 112 get them in the end anyway.  If you have a question about something
 113 in the PNG specification that is related to using libpng, send it
 114 to me.  Send me any questions that start with "I was using libpng,
 115 and ...".  If in doubt, send questions to me.  I'll bounce them
 116 to others, if necessary.
 117
 118 Please do not send suggestions on how to change PNG.  We have
 119 been discussing PNG for three years now, and it is official and
 120 finished.  If you have suggestions for libpng, however, I'll
 121 gladly listen.  Even if your suggestion is not used for version
 122 1.0, it may be used later.
 123
 124 Files in this distribution:
 125
 126       CHANGES       =>  Description of changes between libpng versions
 127       README        =>  This file
 128       TODO          =>  Things not implemented in the current library
 129       ansi2knr.1    =>  Manual page for ansi2knr
 130       ansi2knr.c    =>  Converts files to K&R style function declarations
 131       build.bat     =>  MS-DOS batch file for Borland compiler
 132       descrip.mms   =>  VMS project file
 133       example.c     =>  Example code for using libpng functions
 134       libpng.3      =>  manual page for libpng
 135       libpng.txt    =>  Description of libpng and its functions
 136       libpngpf.3    =>  manual page for libpng's private functions
 137       png.5         =>  manual page for the PNG format
 138       png.c         =>  Basic interface functions common to library
 139       png.h         =>  Library function and interface declarations
 140       pngconf.h     =>  System specific library configuration
 141       pngerror.c    =>  Error/warning message I/O functions
 142       pngget.c      =>  Functions for retrieving info from struct
 143       pngmem.c      =>  Memory handling functions
 144       pngpread.c    =>  Progressive reading functions
 145       pngread.c     =>  Read data/helper high-level functions
 146       pngrio.c      =>  Lowest-level data read I/O functions
 147       pngrtran.c    =>  Read data transformation functions
 148       pngrutil.c    =>  Read data utility functions
 149       pngset.c      =>  Functions for storing data into the info_struct
 150       pngtest.c     =>  Library test program
 151       pngtest.png   =>  Library test sample image
 152       pngtrans.c    =>  Common data transformation functions
 153       pngwio.c      =>  Lowest-level write I/O functions
 154       pngwrite.c    =>  High-level write functions
 155       pngwtran.c    =>  Write data transformations
 156       pngwutil.c    =>  Write utility functions
 157       scripts       =>  Directory containing scripts for building libpng:
 158         descrip.mms   =>  VMS makefile for MMS or MMK
 159         makefile.std  =>  Generic UNIX makefile
 160         makefile.knr  =>  Archaic UNIX Makefile that converts files with ansi2knr
 161         makefile.dec  =>  DEC Alpha UNIX makefile
 162         makefile.sgi  =>  Silicon Graphics IRIX makefile
 163         makefile.sun  =>  Sun makefile
 164         makefile.s2x  =>  Solaris 2.X makefile (gcc, creates libpng.so.2.1.0)
 165         makefile.lnx  =>  Linux/ELF makefile (gcc, creates libpng.so.2.1.0)
 166         makefile.mip  =>  MIPS makefile
 167         makefile.aco  =>  Acorn makefile
 168         makefile.ama  =>  Amiga makefile
 169         smakefile.ppc =>  AMIGA smakefile for SAS C V6.58/7.00 PPC compiler
 170                           (Requires SCOPTIONS, copied from scripts/SCOPTIONS.ppc)
 171         makefile.atr  =>  Atari makefile
 172         makefile.bor  =>  Borland makefile
 173         build.bat     =>  MS-DOS batch file for Borland compiler
 174         makefile.dj2  =>  DJGPP 2 makefile
 175         makefile.msc  =>  Microsoft C makefile
 176         makefile.tc3  =>  Turbo C 3.0 makefile
 177         makefile.os2  =>  OS/2 Makefile (gcc and emx, requires pngos2.def)
 178         makefile.wat  =>  Watcom 10a+ Makefile, 32-bit flat memory model
 179         pngos2.def    =>  OS/2 module definition file used by makefile.os2
 180         makevms.com   =>  VMS build script
 181
 182 Good luck, and happy coding.
 183
 184 -Glenn Randers-Pehrson
 185  Internet: randeg@alumni.rpi.edu
 186  Web: http://www.rpi.edu/~randeg/index.html
 187
 188 -Andreas Eric Dilger
 189  Internet: adilger@enel.ucalgary.ca
 190  Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/
 191
 192 -Guy Eric Schalnat
 193  (formerly of Group 42, Inc)
 194  Internet: gschal@infinet.com