A Thinning-free Algorithm for Straight Edge Detection in a Gray-scale Image

An efficient algorithm to detect the straight edges present in a gray-scale image is proposed. Algorithms to detect curvilinear edges (of possibly uneven thickness) and algorithms to segment a one-pixel thick digital curve into a sequence of straight pieces are found in the literature in several varieties and in several paradigms. However, to the best of our knowledge, there exists no algorithm till date that can detect straight edges in a gray-scale image without thinning. The proposed algorithm uses the novel idea of exponential averaging to achieve a carry-forward of previous edge strengths along the traversed straight edge. The process is computationally attractive, since the underlying operations at an edge point effectively reduce to one right shift and one integer addition. The straightness of an edge is verified from classical chain code properties realizable by simple integer operations, thereby making the algorithm easy for implementation and fast in execution. Experimental results demonstrate its efficiency and robustness.