Single pass algorithm for the generation of chain-coded contours and contours inclusion relationship

A single-pass algorithm for extracting 8-direction chain-coded contours from a binary image and determining the contour inclusion relationship is described. The algorithm processes the image using a 2 × 2 pixel window sliding in a raster scanning fashion. By observing the sequence of patterns through this window, intermediate structures called fragments may be created, lengthened, merged, or closed to form a complete contour. Inclusion relationships among fragments and/or contour are maintained throughout the processing, and are operated in such a way that, once a contour is formed, its relationship with those contours being enclosed must be correct. Realization of the algorithm on a sequential machine is compared with other algorithms in the literature, showing that, for images with more contour points, the proposed algorithm is the fastest