IMAGE DECODING APPARATUS

PURPOSE: An image dequantizing method is provided to enhance the subjective image quality which is restored by making the color difference between domains a little bit by classifying the image into each area and making the amount of change of the quantization coefficient of which the each area is used in the chromaticity component smaller than in the luminance component. CONSTITUTION: The image decoder device comprises an entropy decoding part, inverse quantizer, and image recovery part. The entropy decoding part(109) decodes the bit string into the entropy. The inverse quantizer(111) determines a first quantization coefficient of the macro blocks included in a first area by using the quantization information and the additional quantization information of the magnetic domain included in the one header among the entropy decoded information. The inverse quantizer performs the inverse quantization of the macro blocks included in the first area by using the determined first quantization coefficient. The inverse quantizer obtains the second quantization coefficient of the macro blocks included in the second area through the quantization information of the magnetic domain. The inverse quantizer performs the inverse quantization of the macro blocks included in the second part by using the second quantization coefficient. The image recovery part(112) inversed-transforms the dequantized macro blocks and decodes the image.