Ridges and valleys on digital images

Abstract

Ridges and valleys on digital images are found by looking for zero crossings of the first directional derivative taken in a direction which extremizes the second directional derivative. Computation of the required directional derivative is accomplished by fitting a two-variable cubic polynomial to each neighborhood of the image. Results are shown for a face image and an airphoto scene. It indicates that the technique has a good ability to find ridges and valleys.