pngquant is a command-line utility and a library for lossy compression of PNG images.
The conversion reduces file sizes significantly (often as much as 70%) and preserves full alpha transparency. Generated images are compatible with all modern web browsers, and have better fallback in IE6 than 24-bit PNGs.
GUI QT开发的,支持windows和mac os
git clone git://github.com/pornel/pngquant.git