Watershed segmentation is a region-growing method. In watershed segmentation,using gradient image catchment basins represent the regions of the segmentation

segmentation algorithm

This is a paper discribing a fast matting method. It uses a large kernal matting laplacian. A KD-Tree trimap segmentation is also used to decide the size of the kernal.

This Matlab/C code contains routines to perform level set image segmentation according to: (1) various multiphase (multiregion) formulations, including a fast scheme where the computation load grows linearly with the number of regions and,