I too have been playing with color quantization as an exercise so I won't like at your library as I've been trying to do it all on my own and don't want to see other approaches yet, but here he is not quantizing them so his is going to be faster. Also there really is a trade off in trying to reduce the number of pixels and then clustering versus just clustering on them all. How many times you loop and how much those loops costs isn't as cut and dry as I thought.
