I. Introduction
Image segmentation consists of partitioning the image in homogeneous regions, where the pixels within these regions have coherent features such as gray level, color value, texture parameters, and depth to name a few. In some cases, image segmentation can have the purpose of extracting objects from the image based on the low-level physical properties that image pixels represent. A great deal of work has been done in image segmentation over the past decades and the proposed methods include region-based, contour-based, thresholding-based, watershed-based, and clustering-based methods.