Segmentation

Abstract

All image processing operations discussed so far have helped us to “recognize” objects of interest, i. e., to find suitable local features which allow us to distinguish them from other objects and from the background. The next step is to check each individual pixel whether it belongs to an object of interest or not. This operation is called segmentation and produces a binary image. A pixel has the value one if it belongs to the object; otherwise it is zero. Segmentation is the operation at the threshold between low-level image processing and the operations which analyze the shape of objects, such as those discussed in chapter 11. In this chapter, we discuss several types of segmentation meth­ods. Basically we can think of three concepts for segmentation. Pixel-based methods only use the gray values of the individual pixels. Edge-based methods detect edges and then try to follow the edges. Finally, region-based methods analyze the gray values in larger areas.