I finally was able to make a good algorithm to transform images to allRGB. It has take a lot of work, a lot of trial and fail, a lot of investigation and different aproachs to obtain the very best image possible. Keys for this algorithm are: genetic (evolutive) algorithm, make use of RGB and Lab color spaces, and gaussian dithering (It uses a 7x7 matrix of error dispersion). Next improvements: multithreading and CUDA processing (speed improvements). Right now, It takes two days to compute a good image. I want to reduce it to 30 minutes or less whith the same or better quality.