BLOCK-BASED IMAGE COMPRESSION METHOD AND APPARATUS

摘要

A block-based image compression method and encoder/decoder circuit compresses a plurality of pixels having corresponding original color values and luminance values in a block according to different modes of operation. The encoding circuit includes a luminance-level- based representative color generator to generate representative color values for each of a plurality of luminance levels derived from the corresponding luminance levels to produce at least a block color offset value and a quantization value. According to mode zero, each of the pixels in the block is associated with one of the plurality of generated representative color values to generate error map values and a mode zero color error value. According to mode one, representative color values for each of at least three luminance levels are also generated to produce at least three representative color values, corresponding bitmap values and a mode one color error value. A mode based compressed data generator is capable of operating in mode zero and/or one and produces block color mode zero data when the mode zero color error value is less than the mode one color error value, otherwise block color mode one data.