Color information for region segmentation

In color image processing various kinds of color features can be calculated from the tristimuli R, G, and B. We attempt to derive a set of effective color features by systematic experiments of region segmentation. An Ohlander-type segmentation algorithm by recursive thresholding is employed as a tool for the experiment. At each step of segmenting a region, new color features are calculated for the pixels in that region by the Karhunen Loeve transformation of R, G, and B data. By analyzing more than 100 color features which are thus obtained during segmenting eight kinds of color pictures, we have found that a set of color features, (R + G + B)3, R - B, and (2G - R - B)3, are effective. These three features are significant in this order and in many cases a good segmentation can be achieved by using only the first two. The effectiveness of our color feature set is discussed by a comparative study with various other sets of color features which are commonly used in image analysis. The comparison is performed in terms of both the quality of segmentation results and the calculation involved in transforming data of R, G, and B to other forms.