This package is based on the package 'pngnq' from project 'graphics'.

Pngnq is a tool for quantizing 32-bit RGBA PNG images to 8-bit RGBA pallete
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.