Pngnq is a tool for quantizing 32-bit RGBA PNG images to 8-bit RGBA palette PNG. It's is an adaptation by Stuart Coyle of Greg Roelf's pnqquant. While pngquant uses a median cut algorithm, Pngnq uses Anthony Dekker's neuquant algorithm (http://members.ozemail.com.au/~dekker/NEUQUANT.HTML), generally resulting in better looking results than pngquant.

Optimizers (like pngcrush and optipng) optimize the compression, usually losslessly. pngnq quantizes colors down to 256 (or fewer) distinct RGBA combinations, which is quite lossy. Optimized PNGs are usually two to four times smaller than the 32-bit versions.