1. INTRODUCTION
Image segmentation aims to partition an image into a set of nonoverlapping regions so that pixels within the same region are homogeneous with respect to some characteristic (e.g., greyvalue or roughness), while pixels from adjacent regions are significantly different with respect to the same characteristic. It is a fundamental problem in image processing, as very often it is necessary to group the highly localized pixels into more global and meaningful segmented objects to facilitate the extraction of useful information. In this paper greyvalue is the image characteristic that forms the basis for segmentation.