This book considers the algorithms of image clustering, approximation, flood-filling, thinning, segmentation, and image transformation. It shows how approximation helps to determine coordinates of segmentation levels that are a base to select the main objects of attention, and details how approximation and distributed cumulative histograms can be applied to face images to detect useful features in the recognition systems. This book will be useful for students, engineers, and scientists interested in computers and information technology, and for anyone interested in images and their role in information systems.