
computationally less expensive and often yields better results. There are many
derivative operators designed for 2-D edge detection, most of which can be
categorized as gradient-based or Laplacian-based methods. The gradient-based
methods detect the edges by looking for the maximum in the first derivative of
the image. The Laplacian-based methods search for zero-crossings in the second
derivative of the image to find edges.
9.3.2 Boundary Tracking Based on
Maximum Gradient Magnitude
Because object or region boundaries are associated with high gradient magni-
tudes, one can track the boundaries based on the information in a gradient
magnitude image. Suppose ...