Watershed Segmentation

Hang XiaoJan 25, 2013

Idea

• Region-based segmentation approach– a landscape or topographic relief which is flooded

by water– watersheds are the dividing lines of the domains

of attraction of rain falling over the region– Basins: local minima– Watershed lines : dams

Algorithm (Vincent and Soile)

1. Generate a list of all pixels in the image in height order.2. Pixels belonging to the minimum are labeled with different

identifier and placed into a FIFO queue3. Loop until all pixels are visited– Removed the top pixel from the queue and put its unvisited neighbors

into the queue– For the top pixel label it

• if its neighboring have only one kind of labeled identifier, label it with the same identifier

• Else label it with watershed line3 2 2

3 1 1

0 1 0

3 2 2

3 1 1

A 1 B

h = 0

3 2 2

3 W B

A W B

3 B B

3 B B

A W B

h = 1 h = 2

B B B

W B B

A W B

h = 3

Example