I stumbled upon the color quantization problem while doing something related for work. I then found an interesting paper for which I could find no implementations online, and the thing went from "let's implement this paper" to getting pretty obsessed with the whole thing.
It's at an early, eaaaarly stage. There's a lot of work to be done, and it's a memory hog, but generally speaking works quite well, and the output is for the most part very high quality, so I'm happy to share it as beta.