  In this paper, we formulate a simple algorithm that detects contours around a
region of interest in an image. After an initial smoothing, the method is based
on viewing an image as a topographic surface and finding convex and/or concave
regions using simple calculus-based testing. The algorithm can achieve
multi-scale contour detection by altering the initial smoothing. We show that
the method has promise by comparing results on several images with the
watershed transform performed on the gradient images.
