pngquant is a command-line* utility to quantize and dither 32-bit RGBA PNGs down to 8-bit (or smaller) RGBA-palette PNGs, usually with a significant reduction in file size. (Other PNG image types, even colormapped images, may also be processed, but they will first be expanded to RGBA, which isn't the most efficient way to do so.) This is the same technique used for many of the images on the Miscellaneous Transparent PNGs page, and the results are often indistinguishable from the original, truecolor PNG images.

*Per Fahlén and Jens Wedin made available a Windows GUI wrapper for pngquant called Manfred (binary only). Kornel Lesiński not only created a Mac OS X GUI called ImageAlpha, he also incorporated the NeuQuant algorithm from pngnq; full Python source code is available.

New Maintainer

Alas, Greg's spare time for PNG hacking largely evaporated around the time version 1.0 came out, but the good news is that Kornel Lesiński has been making numerous excellent improvements all along and, as of November 2011, is now officially the new pngquant maintainer. His pngquant page is here:

new pngquant home page

...and he has a similar page for his work on pngnq, which uses a different (and frequently better) quantization algorithm. The two are already merged in his Mac GUI version, ImageAlpha; perhaps that will happen soon for the command-line version, too.

Version 1.0 supported batch processing (i.e., wildcard multifile capability: "pngquant 256 *.png"), palette (tRNS) optimization, and Unix-style filter operation (e.g., "make_RGBA_png | pngquant 48 | some_other_command"), and it compiled and ran on both Linux and Win32 without obvious problems.

Current version: 1.5 or later
Authors: Greg Roelofs, Kornel Lesiński, Jef Poskanzer
License: Open Source
Platforms: Unix, DOS, OS/2, Windows, Macintosh, Amiga, etc.
README: local web site
ChangeLog: local web site
Binaries: Linux x86/glibc   (site 2)   [96k]
Linux x86/libc5   (site 2)   [113k]
Windows 9x/NT/etc.   (site 2)   [109k]
Source code: (.tgz) (.zip) (.tgz) (.zip)
Supporting libraries: libpng

[primary site hosted by] Last modified 27 November 2011.

Copyright © 2000-2005,2011 Greg Roelofs.