[epi 19.1] creat photo mosaics
Steps:
partition image into s*s-sized squares
compute average color of each square
find the tile that is clostest to it in color space.
In essence, the problem reduces to finding the closest point from a set of points in k-d space.
Tips for optimization:
index the tiles using an appropriate search tree
find the matching in parallel by partitioning the original image into subimages and do matching