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 Miscel