The Android Open Source Project | 893912b | 2009-03-03 19:30:05 -0800 | [diff] [blame^] | 1 | =========================== |
| 2 | PNG: The Definitive Guide |
| 3 | =========================== |
| 4 | |
| 5 | Source Code |
| 6 | |
| 7 | Chapters 13, 14 and 15 of "PNG: The Definitive Guide" discuss three free, |
| 8 | cross-platform demo programs that show how to use the libpng reference |
| 9 | library: rpng, rpng2 and wpng. rpng and rpng2 are viewers; the first is |
| 10 | a very simple example that that shows how a standard file-viewer might use |
| 11 | libpng, while the second is designed to process streaming data and shows |
| 12 | how a web browser might be written. wpng is a simple command-line program |
| 13 | that reads binary PGM and PPM files (the ``raw'' grayscale and RGB subsets |
| 14 | of PBMPLUS/NetPBM) and converts them to PNG. |
| 15 | |
| 16 | The source code for all three demo programs currently compiles under |
| 17 | Unix, OpenVMS, and 32-bit Windows. (Special thanks to Martin Zinser, |
| 18 | zinser@decus.de, for making the necessary changes for OpenVMS and for |
| 19 | providing an appropriate build script.) Build instructions can be found |
| 20 | below. |
| 21 | |
| 22 | Files: |
| 23 | |
| 24 | README this file |
| 25 | LICENSE terms of distribution and reuse (BSD-like or GNU GPL) |
| 26 | COPYING GNU General Public License (GPL) |
| 27 | |
| 28 | Makefile.unx Unix makefile |
| 29 | Makefile.w32 Windows (MSVC) makefile |
| 30 | makevms.com OpenVMS build script |
| 31 | |
| 32 | rpng-win.c Windows front end for the basic viewer |
| 33 | rpng-x.c X Window System (Unix, OpenVMS) front end |
| 34 | readpng.c generic back end for the basic viewer |
| 35 | readpng.h header file for the basic viewer |
| 36 | |
| 37 | rpng2-win.c Windows front end for the progressive viewer |
| 38 | rpng2-x.c X front end for the progressive viewer |
| 39 | readpng2.c generic back end for the progressive viewer |
| 40 | readpng2.h header file for the progressive viewer |
| 41 | |
| 42 | wpng.c generic (text) front end for the converter |
| 43 | writepng.c generic back end for the converter |
| 44 | writepng.h header file for the converter |
| 45 | |
| 46 | toucan.png transparent PNG for testing (by Stefan Schneider) |
| 47 | |
| 48 | Note that, although the programs are designed to be functional, their |
| 49 | primary purpose is to illustrate how to use libpng to add PNG support to |
| 50 | other programs. As such, their user interfaces are crude and definitely |
| 51 | are not intended for everyday use. |
| 52 | |
| 53 | Please see http://www.libpng.org/pub/png/pngbook.html for further infor- |
| 54 | mation and links to the latest version of the source code, and Chapters |
| 55 | 13-15 of the book for detailed discussion of the three programs. |
| 56 | |
| 57 | Greg Roelofs |
| 58 | http://pobox.com/~newt/greg_contact.html |
| 59 | 16 March 2008 |
| 60 | |
| 61 | |
| 62 | BUILD INSTRUCTIONS |
| 63 | |
| 64 | - Prerequisites (in order of compilation): |
| 65 | |
| 66 | - zlib http://zlib.net/ |
| 67 | - libpng http://www.libpng.org/pub/png/libpng.html |
| 68 | - pngbook http://www.libpng.org/pub/png/book/sources.html |
| 69 | |
| 70 | The pngbook demo programs are explicitly designed to demonstrate proper |
| 71 | coding techniques for using the libpng reference library. As a result, |
| 72 | you need to download and build both zlib (on which libpng depends) and |
| 73 | libpng. A common build setup is to place the zlib, libpng and pngbook |
| 74 | subdirectory trees ("folders") in the same parent directory. Then the |
| 75 | libpng build can refer to files in ../zlib (or ..\zlib or [-.zlib]), |
| 76 | and similarly for the pngbook build. |
| 77 | |
| 78 | Note that all three packages are designed to be built from a command |
| 79 | line by default; those who wish to use a graphical or other integrated |
| 80 | development environments are on their own. |
| 81 | |
| 82 | |
| 83 | - Unix: |
| 84 | |
| 85 | Unpack the latest pngbook sources (which should correspond to this |
| 86 | README file) into a directory and change into that directory. |
| 87 | |
| 88 | Copy Makefile.unx to Makefile and edit the PNG* and Z* variables |
| 89 | appropriately (possibly also the X* variables if necessary). |
| 90 | |
| 91 | make |
| 92 | |
| 93 | There is no "install" target, so copy the three executables somewhere |
| 94 | in your path or run them from the current directory. All three will |
| 95 | print a basic usage screen when run without any command-line arguments; |
| 96 | see the book for more details. |
| 97 | |
| 98 | |
| 99 | - Windows: |
| 100 | |
| 101 | Unpack the latest pngbook sources (which should correspond to this |
| 102 | README file) into a folder, open a "DOS shell" or "command prompt" |
| 103 | or equivalent command-line window, and cd into the folder where you |
| 104 | unpacked the source code. |
| 105 | |
| 106 | For MSVC, set up the necessary environment variables by invoking |
| 107 | |
| 108 | %devstudio%\vc\bin\vcvars32.bat |
| 109 | |
| 110 | where where %devstudio% is the installation directory for MSVC / |
| 111 | DevStudio. If you get "environment out of space" errors under 95/98, |
| 112 | create a desktop shortcut with "c:\windows\command.com /e:4096" as |
| 113 | the program command line and set the working directory to the pngbook |
| 114 | directory. Then double-click to open the new DOS-prompt window with |
| 115 | a bigger environment and retry the commands above. |
| 116 | |
| 117 | Copy Makefile.w32 to Makefile and edit the PNGPATH and ZPATH variables |
| 118 | appropriately (possibly also the "INC" and "LIB" variables if needed). |
| 119 | Note that the names of the dynamic and static libpng and zlib libraries |
| 120 | used in the makefile may change in later releases of the libraries. |
| 121 | Also note that, as of libpng version 1.0.5, MSVC DLL builds do not work. |
| 122 | This makefile therefore builds statically linked executables, but if |
| 123 | the DLL problems ever get fixed, uncommenting the appropriate PNGLIB |
| 124 | and ZLIB lines will build dynamically linked executables instead. |
| 125 | |
| 126 | Do the build by typing |
| 127 | |
| 128 | nmake |
| 129 | |
| 130 | The result should be three executables: rpng-win.exe, rpng2-win.exe, |
| 131 | and wpng.exe. Copy them somewhere in your PATH or run them from the |
| 132 | current folder. Like the Unix versions, the two windowed programs |
| 133 | (rpng and rpng2) now display a usage screen in a console window when |
| 134 | invoked without command-line arguments; this is new behavior as of |
| 135 | the June 2001 release. Note that the programs use the Unix-style "-" |
| 136 | character to specify options, instead of the more common DOS/Windows |
| 137 | "/" character. (For example: "rpng2-win -bgpat 4 foo.png", not |
| 138 | "rpng2-win /bgpat 4 foo.png") |
| 139 | |
| 140 | |
| 141 | - OpenVMS: |
| 142 | |
| 143 | Unpack the pngbook sources into a subdirectory and change into that |
| 144 | subdirectory. |
| 145 | |
| 146 | Edit makevms.com appropriately, specifically the zpath and pngpath |
| 147 | variables. |
| 148 | |
| 149 | @makevms |
| 150 | |
| 151 | To run the programs, they probably first need to be set up as "foreign |
| 152 | symbols," with "disk" and "dir" set appropriately: |
| 153 | |
| 154 | $ rpng == "$disk:[dir]rpng-x.exe" |
| 155 | $ rpng2 == "$disk:[dir]rpng2-x.exe" |
| 156 | $ wpng == "$disk:[dir]wpng.exe" |
| 157 | |
| 158 | All three will print a basic usage screen when run without any command- |
| 159 | line arguments; see the book for more details. Note that the options |
| 160 | style is Unix-like, i.e., preceded by "-" rather than "/". |
| 161 | |
| 162 | |
| 163 | RUNNING THE PROGRAMS: (VERY) BRIEF INTRO |
| 164 | |
| 165 | rpng is a simple PNG viewer that can display transparent PNGs with a |
| 166 | specified background color; for example, |
| 167 | |
| 168 | rpng -bgcolor #ff0000 toucan.png |
| 169 | |
| 170 | would display the image with a red background. rpng2 is a progressive |
| 171 | viewer that simulates a web browser in some respects; it can display |
| 172 | images against either a background color or a dynamically generated |
| 173 | background image. For example: |
| 174 | |
| 175 | rpng2 -bgpat 16 toucan.png |
| 176 | |
| 177 | wpng is a purely command-line image converter from binary PBMPLUS/NetPBM |
| 178 | format (.pgm or .ppm) to PNG; for example, |
| 179 | |
| 180 | wpng -time < toucan-notrans.ppm > toucan-notrans.png |
| 181 | |
| 182 | would convert the specified PPM file (using redirection) to PNG, auto- |
| 183 | matically setting the PNG modification-time chunk. |
| 184 | |
| 185 | All options can be abbreviated to the shortest unique value; for example, |
| 186 | "-bgc" for -bgcolor (versus "-bgp" for -bgpat), or "-g" for -gamma. |