Line representation of elongated shapes

In this paper we present an algorithm to obtain a line representation of elongated figures whose main purpose is that of avoiding the distortions introduced by thinning algorithms. This is accomplished by using the information carried by the contour of the ribbons to detect the presence of regions where two ribbons merge or cross, since the distortions mainly affect the lines in correspondence of these regions. Once such a region is detected, the grassfire propagation model used to compute the spine is abandoned and shape preserving criteria are adopted to compute the line within the region. Experimental results show that the lines provided by the algorithm are not affected by the distortions typically present in the lines provided by thinning algorithms. They also show that the algorithm provides a line representation of the figures that can be immediately used to obtain the decomposition of the figure into pieces, each one corresponding to one of the ribbon making up the figure, which is highly desirable in many applications dealing with ribbon like figures