All image processing operations discussed in the Chapters 10-14 aimed at a better recognition of 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 and high-level image processing. With segmentation, we leave the pixel-oriented image data since we decide which pixels belong to an object. Only at this step, we gain knowledge that objects are contained in the image.