SIMULATING THE GRASSFIRE TRANSFORM USING AN ACTIVE CONTOUR MODEL

In this paper, we present a new method for shape description of planar objects that integrates both region and boundary features. Our method is an implementation of a 2-D dynamic grassfire that relies on a distance surface on which elastic contours minimize an energy function. A Euclidean distance transform combined with an active contour model, such as the snake, is used for this minimization process. Boundary information is integrated into the model by the extraction of curvature extrema and arcs of constant curvature. The use of an active contour on a field of grass, represented as a distance surface, combined with the curvature features of the boundary permits us to extract a Euclidean skeleton representation of the shape while bypassing many of the discretization problems found in other skeletonization algorithms. We propose a new concept for skeletal branch significance based on the notion of the local deformation introduced by symmetry points on the distance surface. We call this the ridge support. Furthermore, we show how the ridge support can be evaluated in terms of the velocity of formation of a symmetric axis or in terms of the slope amplitude of a tangent to the symmetric axis. We propose a new concept (the deformable skeleton), which is useful for tracking deformable shapes. We refer to this as the dynamic skeleton.