Quantization to 16 colors with None/Riemersma error dithering

16 Colors	16 Colors + Riemersma
Uniform (2,1,1)
RMSE 130.294	RMSE 168.876
Popularity (3 bits)
RMSE 23.520	RMSE 36.307
Median Cut (8 bits)
RMSE 16.944	RMSE 24.072
Octree (8 bits 2-pass)
RMSE 21.621	RMSE 29.310
Xiaolin Wu v2
RMSE 14.766	RMSE 21.802
Dennis Lee v3 (5 bits)
RMSE 15.104	RMSE 21.179
Binary Split
RMSE 15.041	RMSE 20.879
Lloyd (K-Means)
RMSE 14.073	RMSE 19.890
NeuQuant (200 cycles)
RMSE 14.278	RMSE 20.244
SColorQ
RMSE 26.085