My new post: Sparse Field Active Contours
implements quicker, more accurate active contours.
The well-known Chan-Vese segmentation algorithm from the paper “Active Contours Without Edges,” is a great example of active contours. This technique deforms an initial curve so that it separates foreground from background based on the means of the two regions. The technique is very robust to initialization and gives very nice results when there is a difference between the foreground and background means.
In this video, the curve begins as a square. As time goes on the square changes shape so that it does a better and better job of separating the image into a light area and a dark area.
Below is a download-able Matlab demo. The code is very easy to read, and could be the foundation for lots of other active contour segmentation techniques.