APPARATUS FOR COMPRESSION-CODING IMAGE DATA AND METHOD OF THE SAME BASED ON QUANTIFICATION AND FREQUENCY TRANSFORM COEFFICIENT AMPLITUDE REDUCTION

An image compression-coding device includes a level conversion circuit for adaptively reducing the amplitude of the quantification coefficient data based on statistical characteristics of the quantification coefficient data. The device further includes a selection circuit for selectively outputting either the quantification coefficient data after the level conversion or the quantification coefficient data before the level conversion, so that the image compression-coding device outputs a smaller amount of variable-length codes.