They however rely on user interaction, and as such are not very suitable for fully automated target extraction. We shall next take a deeper look into discrete representation. Its main function is to yield scale invariant internal energy. The internal energy is usually also translation and rotation invariant. Image energy at each point pi is related to the properties of image in that particular point.
Interesting properties are, for example, intensity of image and intensity change of the image.
Assume now that we interested in edges in the image. O we still have to minimize the defined energy. This is not an easy thing to do, because the external energy function is typically highly nonlinear, and we would like to find the global minimum or at least a strong local minimum. Call the result C 2 . See if the given convergence criterion is satisfied.