The simple implementation of Structure-Aware Halftone.

Page: http://www.cse.cuhk.edu.hk/~ttwong/papers/structurehalftone/structurehalftone.html

I modified the method.

1. the origin algorithm init the halftone image using random distribution of black and white points; I init it using [Ostromoukhov 2001].

2. The origin method randomly swaps an arbitrary pair of black and white pixels in the image; while I swap the black and white pixels within a small k by k block and run for all the blocks.

3. They use an anneal-like algorothm, I think a single pass is enough, for that the time consumption is very expensive.