We are almost at the end of our chapter on edge detection. Before we close off the topic, I want to stress a practical aspect concerning edge detection algorithms. While talking about image filtering in Chapter 2, Image Filtering we discussed image noise. We said that noise in an image is not that uncommon and can occur due to a variety of factors. In this section, we're going to look at image noise with reference to edge detection.
So far, we have learned that edge detection algorithms rely on detecting abrupt changes in pixel intensity values. Now try to think of the effect that noise has on the pixel values in an image. It can do two things:
It can change the intensity of the group of pixels in an otherwise uniform area of the original image in such a manner that it becomes considerably different from its surroundings, thereby getting classified as an edge.
It can alter the intensity values of the pixels that actually belong to edges or regions near the edges...