README for libpng 1.0.9 - January 31, 2001 (shared library 2.1)See the note about version numbers near the top of png.hSee INSTALL for instructions on how to install libpng.Libpng comes in two distribution formats.  Get libpng-*.tar.gz if youwant UNIX-style line endings in the text files, or lpng*.zip if you wantDOS-style line endings.Version 0.89 was the first official release of libpng.  Don't let thefact that it's the first release fool you.  The libpng library has been inextensive use and testing since mid-1995.  By late 1997 it hadfinally gotten to the stage where there hadn't been significantchanges to the API in some time, and people have a bad feeling aboutlibraries with versions < 1.0.  Version 1.0.0 was released inMarch 1998.****Note that some of the changes to the png_info structure render thisversion of the library binary incompatible with libpng-0.89 orearlier versions if you are using a shared library.  The type of the"filler" parameter for png_set_filler() has changed from png_byte topng_uint_32, which will affect shared-library applications that usethis function.To avoid problems with changes to the internals of png_info_struct,new APIs have been made available in 0.95 to avoid direct applicationaccess to info_ptr.  These functions are the png_set_<chunk> andpng_get_<chunk> functions.  These functions should be used whenaccessing/storing the info_struct data, rather than manipulating itdirectly, to avoid such problems in the future.It is important to note that the APIs do not make current programsthat access the info struct directly incompatible with the newlibrary.  However, it is strongly suggested that new programs usethe new APIs (as shown in example.c and pngtest.c), and older programsbe converted to the new format, to facilitate upgrades in the future.****Additions since 0.90 include the ability to compile libpng as aWindows DLL, and new APIs for accessing data in the info struct.Experimental functions include the ability to set weighting and costfactors for row filter selection, direct reads of integers from bufferson big-endian processors that support misaligned data access, fastermethods of doing alpha composition, and more accurate 16->8 bit colorconversion.The additions since 0.89 include the ability to read from a PNG streamwhich has had some (or all) of the signature bytes read by the callingapplication.  This also allows the reading of embedded PNG streams thatdo not have the PNG file signature.  As well, it is now possible to setthe library action on the detection of chunk CRC errors.  It is possibleto set different actions based on whether the CRC error occurred in acritical or an ancillary chunk.The changes made to the library, and bugs fixed are based on discussionson the PNG implementation mailing list <png-implement@ccrc.wustl.edu>and not on material submitted privately to Guy, Andreas, or Glenn.  They willforward any good suggestions to the list.For a detailed description on using libpng, read libpng.txt.  Forexamples of libpng in a program, see example.c and pngtest.c.  For usageinformation and restrictions (what little they are) on libpng, seepng.h.  For a description on using zlib (the compression library used bylibpng) and zlib's restrictions, see zlib.hI have included a general makefile, as well as several machine andcompiler specific ones, but you may have to modify one for your own needs.You should use zlib 1.0.4 or later to run this, but it MAY work withversions as old as zlib 0.95.  Even so, there are bugs in older zlibversions which can cause the output of invalid compression streams forsome images.  You will definitely need zlib 1.0.4 or later if you aretaking advantage of the MS-DOS "far" structure allocation for the smalland medium memory models.  You should also note that zlib is acompression library that is useful for more things than just PNG files.You can use zlib as a drop-in replacement for fread() and fwrite() ifyou are so inclined.zlib should be available at the same place that libpng is.If not, it should be at ftp.uu.net in /graphics/pngEventually, it will be at ftp.uu.net in /pub/archiving/zip/zlibYou may also want a copy of the PNG specification.  It is availableas an RFC and a W3C Recommendation.  Failingthese resources you can try ftp.uu.net in the /graphics/png directory.This code is currently being archived at ftp.uu.net in the/graphics/png directory, and on CompuServe, Lib 20 (PNG SUPPORT)at GO GRAPHSUP.  If you can't find it in any of those places,e-mail me, and I'll help you find it.If you have any code changes, requests, problems, etc., please e-mailthem to me.  Also, I'd appreciate any make files or project files,and any modifications you needed to make to get libpng to compile,along with a #define variable to tell what compiler/system you are on.If you needed to add transformations to libpng, or wish libpng wouldprovide the image in a different way, drop me a note (and code, ifpossible), so I can consider supporting the transformation.Finally, if you get any warning messages when compiling libpng(note: not zlib), and they are easy to fix, I'd appreciate thefix.  Please mention "libpng" somewhere in the subject line.  Thanks.This release was created and will be supported by myself (of coursebased in a large way on Guy's and Andreas' earlier work), and the PNG group.randeg@alum.rpi.edupng-implement@ccrc.wustl.eduYou can't reach Guy, the original libpng author, at the addressesgiven in previous versions of this document.  He and Andreas will read mailaddressed to the png-implement list, however.Please do not send general questions about PNG.  Send them tothe address in the specification (png-group@w3.org).  At the sametime, please do not send libpng questions to that address, send them to meor to png-implement@ccrc.wustl.edu.  I'llget them in the end anyway.  If you have a question about somethingin the PNG specification that is related to using libpng, send itto me.  Send me any questions that start with "I was using libpng,and ...".  If in doubt, send questions to me.  I'll bounce themto others, if necessary.Please do not send suggestions on how to change PNG.  We havebeen discussing PNG for three years now, and it is official andfinished.  If you have suggestions for libpng, however, I'llgladly listen.  Even if your suggestion is not used for version1.0, it may be used later.Files in this distribution:      ANNOUNCE      =>  Announcement of this version, with recent changes      CHANGES       =>  Description of changes between libpng versions      KNOWNBUG      =>  List of known bugs and deficiencies      LICENSE       =>  License to use and redistribute libpng      README        =>  This file      TODO          =>  Things not implemented in the current library      Y2KINFO       =>  Statement of Y2K compliance      example.c     =>  Example code for using libpng functions      libpng.3      =>  manual page for libpng (includes libpng.txt)      libpng.txt    =>  Description of libpng and its functions      libpngpf.3    =>  manual page for libpng's private functions      png.5         =>  manual page for the PNG format      png.c         =>  Basic interface functions common to library      png.h         =>  Library function and interface declarations      pngconf.h     =>  System specific library configuration      pngasmrd.h    =>  Header file for assembler-coded functions      pngerror.c    =>  Error/warning message I/O functions      pngget.c      =>  Functions for retrieving info from struct      pngmem.c      =>  Memory handling functions      pngbar.png    =>  PNG logo, 88x31      pngnow.png    =>  PNG logo, 98x31      pngpread.c    =>  Progressive reading functions      pngread.c     =>  Read data/helper high-level functions      pngrio.c      =>  Lowest-level data read I/O functions      pngrtran.c    =>  Read data transformation functions      pngrutil.c    =>  Read data utility functions      pngset.c      =>  Functions for storing data into the info_struct      pngtest.c     =>  Library test program      pngtest.png   =>  Library test sample image      pngtrans.c    =>  Common data transformation functions      pngwio.c      =>  Lowest-level write I/O functions      pngwrite.c    =>  High-level write functions      pngwtran.c    =>  Write data transformations      pngwutil.c    =>  Write utility functions      contrib       =>  Contributions       gregbook         =>  source code for PNG reading and writing, from                            Greg Roelofs' "PNG: The Definitive Guide",                            O'Reilly, 1999       msvctest     =>  Builds and runs pngtest using a MSVC workspace       pngminus     =>  Simple pnm2png and png2pnm programs       pngsuite     =>  Test images       visupng      =>  Contains a MSVC workspace for VisualPng      projects      =>  Contains project files and workspaces for building DLL       borland          =>  Contains a Borland workspace for building libpng                            and zlib       msvc             =>  Contains a Microsoft Visual C++ (MSVC) workspace                            for building libpng and zlib       wince            =>  Contains a Microsoft Visual C++ (Windows CD Toolkit)                            workspace for building libpng and zlib on WindowsCE      scripts       =>  Directory containing scripts for building libpng:       descrip.mms      =>  VMS makefile for MMS or MMK       makefile.std     =>  Generic UNIX makefile (cc, creates static libpng.a)       makefile.linux   =>  Linux/ELF makefile                            (gcc, creates libpng.so.2.1.0.9)       makefile.gcmmx   =>  Linux/ELF makefile (gcc, creates                            libpng.so.2.1.0.9, uses assembler code                            tuned for Intel MMX platform)       makefile.gcc     =>  Generic makefile (gcc, creates static libpng.a)       makefile.knr     =>  Archaic UNIX Makefile that converts files with                            ansi2knr (Requires ansi2knr.c from                            ftp://ftp.cs.wisc.edu/ghost)       makefile.aix     =>  AIX makefile       makefile.cygwin  =>  Cygwin/gcc makefile       makefile.dec     =>  DEC Alpha UNIX makefile       makefile.hpux    =>  HPUX (10.20 and 11.00) makefile       makefile.ibmc    =>  IBM C/C++ version 3.x for Win32 and OS/2 (static)       makefile.intel   =>  Intel C/C++ version 4.0 and later       libpng.icc       =>  Project file, IBM VisualAge/C++ 4.0 or later       makefile.macosx  =>  MACOS X Makefile       makefile.sgi     =>  Silicon Graphics IRIX (cc, creates static lib)       makefile.sggcc   =>  Silicon Graphics (gcc, creates libpng.so.2.1.0.9)       makefile.sunos   =>  Sun makefile       makefile.solaris =>  Solaris 2.X makefile                            (gcc, creates libpng.so.2.1.0.9)       makefile.sco     =>  For SCO OSr5  ELF and Unixware 7 with Native cc       makefile.mips    =>  MIPS makefile       makefile.acorn   =>  Acorn makefile       makefile.amiga   =>  Amiga makefile       smakefile.ppc    =>  AMIGA smakefile for SAS C V6.58/7.00 PPC                            compiler (Requires SCOPTIONS, copied from                            scripts/SCOPTIONS.ppc)       makefile.atari   =>  Atari makefile       makefile.beos    =>  BEOS makefile for X86       makefile.bor     =>  Borland makefile (uses bcc)       makefile.bc32    =>  32-bit Borland C++ (all modules compiled in C mode)       makefile.bd32    =>  To make a png32bd.dll with Borland C++ 4.5       makefile.tc3     =>  Turbo C 3.0 makefile       makefile.dj2     =>  DJGPP 2 makefile       makefile.msc     =>  Microsoft C makefile       makefile.vcawin32 => makefile for Microsoft Visual C++ 5.0 and                            later (uses assembler code tuned for Intel MMX                            platform)       makefile.vcwin32 =>  makefile for Microsoft Visual C++ 4.0 and                            later (does not use assembler code)       makefile.os2     =>  OS/2 Makefile (gcc and emx, requires pngos2.def)       pngos2.def       =>  OS/2 module definition file used by makefile.os2       makefile.watcom  =>  Watcom 10a+ Makefile, 32-bit flat memory model       makevms.com      =>  VMS build script       pngdef.pas       =>  Defines for a png32bd.dll with Borland C++ 4.5       SCOPTIONS.ppc    =>  Used with smakefile.ppcGood luck, and happy coding.-Glenn Randers-Pehrson Internet: randeg@alum.rpi.edu-Andreas Eric Dilger Internet: adilger@enel.ucalgary.ca Web: http://www-mddsp.enel.ucalgary.ca/People/adilger/-Guy Eric Schalnat (formerly of Group 42, Inc) Internet: gschal@infinet.com