Thicken pixels with high gradients

Thickness control

Simple renderer

Should work on after effects now

It's sure it is good for hairy contents. I am not sure if those images will be  easier cases for classical mosaic methods or not. I am thinking to use Barbara's examples to guide color choices and shape maps.

Different parameters for smoothness and sparseness

Fixed most of doubly edges

The results are without length and direction constraints as previous. Their object boundaries might be crossed sometime. Not sure which way is best to merge the length control and direction control.