| Color quantization is sampling of three dimensional color spaces (such as RGB or Lab), which results in a discrete subset of colors known as a color codebook or palette. It is extensively used for display, transfer, and storage of images in Internet-based applications, computer graphics, and animation. We propose a sampling scheme, which provides a uniform quantization of the Lab color space. The idea is based on several results from number theory and philotaxy. The sampling algortihm is very much systematic, and allows fast quantization and order sither of color images. The display quality of images quantized by the proposed color codebook is comparable witj that of image-dependent quantizers. Most importantly, the quantized images are more amenable to the type of processing used for gray scale ones. Methods for processing gray-scale images cannot be simply extended to color images because they rely on the fact that each gray-level is described by a single number and the fact that a relation of full order can be easily established on the set of those numbers. Color spaces (such as RGB or Lab) are, on the other hand, three-dimensional. The proposed color quantization, i.e., color space sampling and numbering of sampled points, makes the methods for processing gray-scale mages extendible to color images. We illustrate possible processing of color images by first introducing the basic average and difference operators and then implementing edge detection and compression of color quantized images. | |