Method of selecting colors for pixels within blocks for block truncation encoding

A method of selecting colors to be assigned to pixels in an image, comprising the steps of:

• a) dividing the image into a plurality of blocks wherein each block is comprised of a plurality of pixels and each pixel has a value that represents the luminance, chrominance and hue at a discrete location in an image;
• b) identifying at least one largest pixel cluster in a block, wherein said largest pixel cluster includes a largest number of pixels having substantially the same luminance, chrominance, and hue value, said largest pixel cluster being determined as including the largest number of pixels in a pixel value range by:
• b1) performing a histogram analysis of three or more dimensions of said block to designate one or more pixel value ranges, each pixel in said block thereby being assignable to a selected pixel value range,
• b2) associating the pixels assigned to each one or more signal value ranges with a respective one or more clusters,
• b3) determining which of the one or more clusters includes the greatest number of pixels;
• c) designating a largest pixel cluster signal value associated with said largest pixel cluster for a first assignment to said block and setting a value of all pixels in said largest cluster equal to said largest pixel cluster signal value;
• and
• d) calculating an average luminance, chrominance and hue value for pixels outside of said largest pixel cluster, and designating a resulting average outside pixel signal value for a next assignment to said block.