US Patent 7146039 Image compression apparatus and image compression program

An image compression apparatus for compressing image data that includes luminance signal and chrominance signals includes an image judgement part that judges characterizing features of the image data on the basis of the luminance signal and/or chrominance signals, a subsampling rate setting part which sets the subsampling rate of the chrominance signals in accordance with the characterizing features thus judged, a subsampling processing part which performs subsampling processing of the image data at the set subsampling rate, and a compression encoding part which subjects the subsampling-processed image data to compression encoding.