OptiPNG Home Page

OptiPNG: Advanced PNG Optimizer

Current version: OptiPNG 0.4.8 (released 10 May 2005)
Download the source code: optipng-0.4.8.tar.gz, optipng-0.4.8.zip
Download the Windows executable: optipng-0.4.8-exe.zip

What's new (see HISTORY for the complete list of changes):

Fixed reduction bug
Fixed a palette-to-gray reduction problem that occurred when an RGB triple had both an alpha below max, and an alpha equal to max.

OptiPNG is a PNG optimizer that recompresses the image files to a smaller size, without losing any information.
The idea has been inspired from pngcrush (http://pmt.sourceforge.net/pngcrush), and is explained in detail in the PNG-Tech article "A guide to PNG optimization". The implementation is carried forward in OptiPNG, which offers a faster execution per trial, and a wider search space.

The documentation is included in the downloadable archives, and it is also available here:

LICENSE
OptiPNG is open-source software, released under the zlib/libpng license.
FEATURES
The complete list of features.
USAGE
Program usage.
CAVEAT
We cannot, in good conscience, fail to inform the users about the known bugs, problems, or limitations. Caveat Emptore!
DESIGN
Internal documentation: design decisions and rationale.
HISTORY
The program revision history.
TODO
The "to-do" list.

NOTE:
The OptiPNG source distribution contains modified versions of zlib-1.2.2 and libpng-1.0.18. Still, OptiPNG works with the original libraries as well. These libraries are available at their home sites:

zlib at http://www.zlib.net/
A notable change: the constant TOO_FAR is set to 32768, for a slight compression improvement; see the PNG-Tech article "TOO_FAR in zlib is not too far...".
libpng at http://www.libpng.org/pub/png/libpng.html
The modified version provides a small speed improvement. In addition, the unused features are disabled and compiled out, allowing a smaller executable.

IMPORTANT:
Comments and complaints about these library distributions should NOT be addressed to the authors or to the maintainers of the original libraries.
You may use the original libraries instead of those supplied in the source package; however, if you use the supplied ones, it is strongly recommended to link them in statically.

OptiPNG-related utilities

OptiPNG Plus is an enhanced version that provides additional features. This version is not publicly available.
akJ OptiPNG Wrapper, available at http://www.xucker.jpn.org/eclipsercp/optipngwrapper/, is an Eclipse RCP (Rich Client Platform) application.
More related utilities are available in Japanese, at http://www.xucker.jpn.org/keyword/optipng.html.

Last updated: 10 May 2005 by Cosmin Truţa
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