Used simulated annealing to minimize:
(neighbor pixel color distance)^2 + Const (color distance to the target)^2
where I used Const = 4. The method works best for Seurat portrait for obvious reason, and worst for Rubens (my apology for desecrating his work).
Some preliminary article on the method I used is here: http://d.hatena.ne.jp/ita/20100222/p1
All original images are from wikimedia commons.
From left to right, top to bottom:
Gogh, Gauguin, Miro, Monet, Seurat,
Cezanne, Hokusai, Leonardo da Vinci, Mucha,
Chagall, Manet, Renoir, Rubens,
Dali, Millet, Picasso, Seurat.
