On the Canny edge detector

The Canny edge detector is widely used in computer vision to locate sharp intensity changes and to find object boundaries in an image. The Canny edge detector classifies a pixel as an edge if the gradient magnitude of the pixel is larger than those of pixels at both its sides in the direction of maximum intensity change. In this paper we will show that defining edges in this manner causes some obvious edges to be missed. We will also show how to revise the Canny edge detector to improve its detection accuracy.