Patent ID: 6898308

Claim:
An image-processing method comprising: obtaining representations of color values for plural pixels of an image, computing pairwise color averages of at least some pairs of pixels, and storing the color averages, wherein: (a) the color value of each pixel is represented as a color symbol composed from a scalar luminance index and a scalar chrominance index; (b) for each pair of pixels to be averaged, the averaging comprises: (I) converting the luminance index and chrominance index of each pixel to coordinates of a point in a three dimensional color space; (II) obtaining the mean of the resulting two points in the color space, thereby to obtain a mean color value; and (III) quantizing the mean color value; and (c) the quantizing step comprises: (I) selecting a luminance value from a discrete set of quantized luminance values; (II) selecting a chrominance value from an ordered discrete set of quantized chrominance values; (III) composing a representation of the color average from an index of the selected luminance value and an index of an ordinal position of the selected chrominance value; and (IV) storing said representation of the color average.