Hue-based segmentation of color images

In order to decide whether to lump a group of neighboring pixels into a uniform region, image segmentation techniques often rely on the mean and variance of their brightnesses or colors. The paper addresses the problem of using to this end the mean and variance of the hue of a population of pixels. The conventional definitions of these statistics can be misleading because of the angular character of the hue coordinate system, which often splits peaks in hue histograms. The authors present a way of processing hue distributions that avoids this effect. It is based on recursive formulas for calculating the means and variances of hue distributions in an object-dependent coordinate system. At the cost of a slight numerical overhead, these computations generate results in agreement with the authors intuitive understanding of colors in split peak situations, and reduce to the standard definitions in well-behaved histograms. An example of this procedure, and of its integration to an image segmentation algorithm, is given