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libsdl2_image/external/libpng-1.6.37/contrib/gregbook/README
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===========================
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PNG: The Definitive Guide
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===========================
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Source Code
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Chapters 13, 14 and 15 of "PNG: The Definitive Guide" discuss three free,
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cross-platform demo programs that show how to use the libpng reference
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library: rpng, rpng2 and wpng. rpng and rpng2 are viewers; the first is
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a very simple example that that shows how a standard file-viewer might use
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libpng, while the second is designed to process streaming data and shows
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how a web browser might be written. wpng is a simple command-line program
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that reads binary PGM and PPM files (the ``raw'' grayscale and RGB subsets
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of PBMPLUS/NetPBM) and converts them to PNG.
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The source code for all three demo programs currently compiles under
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Unix, OpenVMS, and 32-bit Windows. (Special thanks to Martin Zinser,
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zinser at decus.de, for making the necessary changes for OpenVMS and for
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providing an appropriate build script.) Build instructions can be found
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below.
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Files:
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README this file
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LICENSE terms of distribution and reuse (BSD-like or GNU GPL)
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COPYING GNU General Public License (GPL)
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Makefile.unx Unix makefile
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Makefile.w32 Windows (MSVC) makefile
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makevms.com OpenVMS build script
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rpng-win.c Windows front end for the basic viewer
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rpng-x.c X Window System (Unix, OpenVMS) front end
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readpng.c generic back end for the basic viewer
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readpng.h header file for the basic viewer
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rpng2-win.c Windows front end for the progressive viewer
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rpng2-x.c X front end for the progressive viewer
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readpng2.c generic back end for the progressive viewer
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readpng2.h header file for the progressive viewer
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wpng.c generic (text) front end for the converter
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writepng.c generic back end for the converter
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writepng.h header file for the converter
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toucan.png transparent PNG for testing (by Stefan Schneider)
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Note that, although the programs are designed to be functional, their
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primary purpose is to illustrate how to use libpng to add PNG support to
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other programs. As such, their user interfaces are crude and definitely
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are not intended for everyday use.
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Please see http://www.libpng.org/pub/png/pngbook.html for further infor-
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mation and links to the latest version of the source code, and Chapters
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13-15 of the book for detailed discussion of the three programs.
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Greg Roelofs
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https://pobox.com/~newt/greg_contact.html
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16 March 2008
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BUILD INSTRUCTIONS
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- Prerequisites (in order of compilation):
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- zlib https://zlib.net/
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- libpng http://www.libpng.org/pub/png/libpng.html
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- pngbook http://www.libpng.org/pub/png/book/sources.html
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The pngbook demo programs are explicitly designed to demonstrate proper
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coding techniques for using the libpng reference library. As a result,
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you need to download and build both zlib (on which libpng depends) and
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libpng. A common build setup is to place the zlib, libpng and pngbook
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subdirectory trees ("folders") in the same parent directory. Then the
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libpng build can refer to files in ../zlib (or ..\zlib or [-.zlib]),
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and similarly for the pngbook build.
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Note that all three packages are designed to be built from a command
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line by default; those who wish to use a graphical or other integrated
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development environments are on their own.
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- Unix:
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Unpack the latest pngbook sources (which should correspond to this
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README file) into a directory and change into that directory.
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Copy Makefile.unx to Makefile and edit the PNG* and Z* variables
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appropriately (possibly also the X* variables if necessary).
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make
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There is no "install" target, so copy the three executables somewhere
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in your path or run them from the current directory. All three will
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print a basic usage screen when run without any command-line arguments;
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see the book for more details.
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- Windows:
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Unpack the latest pngbook sources (which should correspond to this
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README file) into a folder, open a "DOS shell" or "command prompt"
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or equivalent command-line window, and cd into the folder where you
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unpacked the source code.
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For MSVC, set up the necessary environment variables by invoking
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%devstudio%\vc\bin\vcvars32.bat
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where where %devstudio% is the installation directory for MSVC /
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DevStudio. If you get "environment out of space" errors under 95/98,
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create a desktop shortcut with "c:\windows\command.com /e:4096" as
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the program command line and set the working directory to the pngbook
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directory. Then double-click to open the new DOS-prompt window with
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a bigger environment and retry the commands above.
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Copy Makefile.w32 to Makefile and edit the PNGPATH and ZPATH variables
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appropriately (possibly also the "INC" and "LIB" variables if needed).
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Note that the names of the dynamic and static libpng and zlib libraries
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used in the makefile may change in later releases of the libraries.
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Also note that, as of libpng version 1.0.5, MSVC DLL builds do not work.
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This makefile therefore builds statically linked executables, but if
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the DLL problems ever get fixed, uncommenting the appropriate PNGLIB
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and ZLIB lines will build dynamically linked executables instead.
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Do the build by typing
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nmake
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The result should be three executables: rpng-win.exe, rpng2-win.exe,
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and wpng.exe. Copy them somewhere in your PATH or run them from the
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current folder. Like the Unix versions, the two windowed programs
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(rpng and rpng2) now display a usage screen in a console window when
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invoked without command-line arguments; this is new behavior as of
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the June 2001 release. Note that the programs use the Unix-style "-"
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character to specify options, instead of the more common DOS/Windows
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"/" character. (For example: "rpng2-win -bgpat 4 foo.png", not
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"rpng2-win /bgpat 4 foo.png")
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- OpenVMS:
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Unpack the pngbook sources into a subdirectory and change into that
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subdirectory.
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Edit makevms.com appropriately, specifically the zpath and pngpath
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variables.
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@makevms
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To run the programs, they probably first need to be set up as "foreign
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symbols," with "disk" and "dir" set appropriately:
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$ rpng == "$disk:[dir]rpng-x.exe"
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$ rpng2 == "$disk:[dir]rpng2-x.exe"
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$ wpng == "$disk:[dir]wpng.exe"
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All three will print a basic usage screen when run without any command-
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line arguments; see the book for more details. Note that the options
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style is Unix-like, i.e., preceded by "-" rather than "/".
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RUNNING THE PROGRAMS: (VERY) BRIEF INTRO
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rpng is a simple PNG viewer that can display transparent PNGs with a
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specified background color; for example,
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rpng -bgcolor \#ff0000 toucan.png
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would display the image with a red background. rpng2 is a progressive
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viewer that simulates a web browser in some respects; it can display
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images against either a background color or a dynamically generated
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background image. For example:
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rpng2 -bgpat 16 toucan.png
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wpng is a purely command-line image converter from binary PBMPLUS/NetPBM
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format (.pgm or .ppm) to PNG; for example,
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wpng -time < toucan-notrans.ppm > toucan-notrans.png
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would convert the specified PPM file (using redirection) to PNG, auto-
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matically setting the PNG modification-time chunk.
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All options can be abbreviated to the shortest unique value; for example,
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"-bgc" for -bgcolor (versus "-bgp" for -bgpat), or "-g" for -gamma.
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