A New Contour Generation Thinning Algorithm

Abstract

Xu and Wang’s Contour Generation Thinning Algorithm is a sequential algorithm as defined by Rosenfeld. It is an iterative procedure where pixels belonging to the contours of the components are processed from a queue of pointers and as a result of the processing, the pointers of new contour pixels are put into another queue. The order in which the contour pixels are placed in and processed from the queue affects the final result. In many instances, spurious end points are generated.

A new algorithm is proposed where the removal condition is related to the idea of multiple pixels. It is a parallel algorithm in which the order of execution of contour pixels will not affect the shape of the skeleton.

A further improvement is in the incorporation of a set of flags in each pixel to denote the direction of propagation of the wave front. The use of these flags reduces the computations involved in determining whether a pixel is multiple or not. After the removal of a non-multiple pixel, the interior pixels which become the new contour can be identified directly using these directions. Furthermore, those interior pixel will inherit these directions and their flags can be set accordingly. In this way, a very efficient algorithm has been constructed.