Active shape model


Active shape models are statistical models of the shape of objects which iteratively deform to fit to an example of the object in a new image, developed by Tim Cootes and Chris Taylor in 1995. The shapes are constrained by the PDM Statistical Shape Model to vary only in ways seen in a training set of labelled examples.
The shape of an object is represented by a set of points. The ASM algorithm aims to match the model to a new image.
The ASM works by alternating the following steps:
The technique has been widely used to analyse images of faces, mechanical assemblies and medical images.
It is closely related to the active appearance model. It is also known as a "Smart Snakes" method, since it is an analog to an active contour model which would respect explicit shape constraints.