Active contour models: overview, implementation and applications

A brief overview of deformable contour models, called snakes, is presented. These energy-minimizing curves are constrained by internal continuity forces (tension and bending) and guided by external image forces toward features. Such a tool can be used in areas such as edge detection, motion tracking, and stereo matching and more generally to solve problems of matching a deformable model to an image by means of energy minimization. The convergence speed has been improved by using parametric B-spline approximations of the curves; the model is called B-snakes. As this approximation can control the degree of continuity at the joints between adjacent curve segments, the B-snakes can have breakpoints and include corners. B-snakes have been applied to the extraction of building tops from aerial images, once a first estimate is obtained from a traditional stereo process