The main issue with any pixel-to-pixel colour mapping approach is that we don't perceive individual pixels so you will not get a good overall effect from pixel-to-pixel mapping (the article touches on this by talking about structure but you don;t have to go that far to see massively improved results).

Any serious attempt would involve higher level dithering to better reproduce the colours of the original image and dithering is one of those topics that goes unexpectedly crazy deep if you are not familiar with the literature.