===========================                      PNG: The Definitive Guide                     ===========================                             Source CodeChapters 13, 14 and 15 of "PNG: The Definitive Guide" discuss three free,cross-platform demo programs that show how to use the libpng referencelibrary:  rpng, rpng2 and wpng.  rpng and rpng2 are viewers; the first isa very simple example that that shows how a standard file-viewer might uselibpng, while the second is designed to process streaming data and showshow a web browser might be written.  wpng is a simple command-line programthat reads binary PGM and PPM files (the ``raw'' grayscale and RGB subsetsof PBMPLUS/NetPBM) and converts them to PNG.The source code for all three demo programs currently compiles underUnix, OpenVMS, and 32-bit Windows.  (Special thanks to Martin Zinser,zinser@decus.de, for making the necessary changes for OpenVMS and forproviding an appropriate build script.)  Build instructions can be foundbelow.Files:   README             this file   LICENSE            terms of distribution and reuse (BSD-like or GNU GPL)   COPYING            GNU General Public License (GPL)   Makefile.unx       Unix makefile   Makefile.w32       Windows (MSVC) makefile   makevms.com        OpenVMS build script   rpng-win.c         Windows front end for the basic viewer   rpng-x.c           X Window System (Unix, OpenVMS) front end   readpng.c          generic back end for the basic viewer   readpng.h          header file for the basic viewer   rpng2-win.c        Windows front end for the progressive viewer   rpng2-x.c          X front end for the progressive viewer   readpng2.c         generic back end for the progressive viewer   readpng2.h         header file for the progressive viewer   wpng.c             generic (text) front end for the converter   writepng.c         generic back end for the converter   writepng.h         header file for the converter   toucan.png         transparent PNG for testing (by Stefan Schneider)Note that, although the programs are designed to be functional, theirprimary purpose is to illustrate how to use libpng to add PNG support toother programs.  As such, their user interfaces are crude and definitelyare not intended for everyday use.Please see http://www.libpng.org/pub/png/pngbook.html for further infor-mation and links to the latest version of the source code, and Chapters13-15 of the book for detailed discussion of the three programs.Greg Roelofshttp://pobox.com/~newt/greg_contact.html2 June 2007BUILD INSTRUCTIONS - Prerequisites (in order of compilation):      - zlib		http://zlib.net/      - libpng		http://www.libpng.org/pub/png/libpng.html      - pngbook		http://www.libpng.org/pub/png/book/sources.html     The pngbook demo programs are explicitly designed to demonstrate proper     coding techniques for using the libpng reference library.  As a result,     you need to download and build both zlib (on which libpng depends) and     libpng.  A common build setup is to place the zlib, libpng and pngbook     subdirectory trees ("folders") in the same parent directory.  Then the     libpng build can refer to files in ../zlib (or ..\zlib or [-.zlib]),     and similarly for the pngbook build.     Note that all three packages are designed to be built from a command     line by default; those who wish to use a graphical or other integrated     development environments are on their own. - Unix:     Unpack the latest pngbook sources (which should correspond to this     README file) into a directory and change into that directory.     Copy Makefile.unx to Makefile and edit the PNG* and Z* variables     appropriately (possibly also the X* variables if necessary).     make     There is no "install" target, so copy the three executables somewhere     in your path or run them from the current directory.  All three will     print a basic usage screen when run without any command-line arguments;     see the book for more details. - Windows:     Unpack the latest pngbook sources (which should correspond to this     README file) into a folder, open a "DOS shell" or "command prompt"     or equivalent command-line window, and cd into the folder where you     unpacked the source code.     For MSVC, set up the necessary environment variables by invoking         %devstudio%\vc\bin\vcvars32.bat     where where %devstudio% is the installation directory for MSVC /     DevStudio.  If you get "environment out of space" errors under 95/98,     create a desktop shortcut with "c:\windows\command.com /e:4096" as     the program command line and set the working directory to the pngbook     directory.  Then double-click to open the new DOS-prompt window with     a bigger environment and retry the commands above.     Copy Makefile.w32 to Makefile and edit the PNGPATH and ZPATH variables     appropriately (possibly also the "INC" and "LIB" variables if needed).     Note that the names of the dynamic and static libpng and zlib libraries     used in the makefile may change in later releases of the libraries.     Also note that, as of libpng version 1.0.5, MSVC DLL builds do not work.     This makefile therefore builds statically linked executables, but if     the DLL problems ever get fixed, uncommenting the appropriate PNGLIB     and ZLIB lines will build dynamically linked executables instead.     Do the build by typing        nmake     The result should be three executables:  rpng-win.exe, rpng2-win.exe,     and wpng.exe.  Copy them somewhere in your PATH or run them from the     current folder.  Like the Unix versions, the two windowed programs     (rpng and rpng2) now display a usage screen in a console window when     invoked without command-line arguments; this is new behavior as of     the June 2001 release.  Note that the programs use the Unix-style "-"     character to specify options, instead of the more common DOS/Windows     "/" character.  (For example:  "rpng2-win -bgpat 4 foo.png", not     "rpng2-win /bgpat 4 foo.png") - OpenVMS:     Unpack the pngbook sources into a subdirectory and change into that     subdirectory.     Edit makevms.com appropriately, specifically the zpath and pngpath     variables.     @makevms     To run the programs, they probably first need to be set up as "foreign     symbols," with "disk" and "dir" set appropriately:     $ rpng  == "$disk:[dir]rpng-x.exe"     $ rpng2 == "$disk:[dir]rpng2-x.exe"     $ wpng  == "$disk:[dir]wpng.exe"     All three will print a basic usage screen when run without any command-     line arguments; see the book for more details.  Note that the options     style is Unix-like, i.e., preceded by "-" rather than "/".RUNNING THE PROGRAMS:  (VERY) BRIEF INTRO     rpng is a simple PNG viewer that can display transparent PNGs with a     specified background color; for example,	rpng -bgcolor #ff0000 toucan.png     would display the image with a red background.  rpng2 is a progressive     viewer that simulates a web browser in some respects; it can display     images against either a background color or a dynamically generated     background image.  For example:	rpng2 -bgpat 16 toucan.png     wpng is a purely command-line image converter from binary PBMPLUS/NetPBM     format (.pgm or .ppm) to PNG; for example,	wpng -time < toucan-notrans.ppm > toucan-notrans.png     would convert the specified PPM file (using redirection) to PNG, auto-     matically setting the PNG modification-time chunk.     All options can be abbreviated to the shortest unique value; for example,     "-bgc" for -bgcolor (versus "-bgp" for -bgpat), or "-g" for -gamma.