=========================== PNG: The Definitive Guide =========================== Source Code Chapters 13, 14 and 15 of "PNG: The Definitive Guide" discuss three free, cross-platform demo programs that show how to use the libpng reference library: rpng, rpng2 and wpng. rpng and rpng2 are viewers; the first is a very simple example that that shows how a standard file-viewer might use libpng, while the second is designed to process streaming data and shows how a web browser might be written. wpng is a simple command-line program that reads binary PGM and PPM files (the ``raw'' grayscale and RGB subsets of PBMPLUS/NetPBM) and converts them to PNG. The source code for all three demo programs currently compiles under Unix, OpenVMS, and 32-bit Windows. (Special thanks to Martin Zinser, [email protected], for making the necessary changes for OpenVMS and for providing an appropriate build script.) Build instructions can be found below. 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, their primary purpose is to illustrate how to use libpng to add PNG support to other programs. As such, their user interfaces are crude and definitely are 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 Chapters 13-15 of the book for detailed discussion of the three programs. Greg Roelofs http://pobox.com/~newt/greg_contact.html 16 March 2008 BUILD 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.