CODER

摘要

PURPOSE:To improve the image quality as an entire pattern by decreasing a compression rate of a block whose image quality deterioration is remarkable visually so as to enhance the compression rate of a block whose image quality deterioration is not remarkable. CONSTITUTION:An input digital image signal including a signal Y and signals R-Y and B-Y respectively is block-processed. Then a signal Y discrimination device 307, an signal R discrimination device 308 and a signal B discrimination device 309 check respectively a level of a luminance signal and color difference signals as to the signal Y and signals R-Y and B-Y and Y discrimination information, discrimination information R and discrimination information B are given to a compression controller 310. The compression controller 310 provides an output of a compression control signal to a quantizer 304 based on the three sets of discrimination information. The quantizer 304 controls a compression rate of color difference signals of each block subject to orthogonal transformation adaptively corresponding to each hue and luminance.