pngquant

Converts 32-bit RGBA PNGs into 8-bit RGBA-palette PNGs

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 (40-70% smaller than 24-bit PNGs). This unique type of PNG supports full alpha transparency and is compatible with all modern web browsers, and has better fallback in IE6 than 24-bit PNGs. Features: - High-quality palette generation using modernized Median Cut algorithm. - Unique dithering algorithm that adds less noise to images than the standard Floyd-Steinberg. - Easy to integrate with shell scripts, GUIs and server-side software. - Fast mode for processing large numbers of images.