IMAGE CODER, IMAGE DECODER AND METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To warrant both an edge position specified with a perceptible resolution and a perceptible number of gray scales and to code an image at high efficiency. SOLUTION: An input image 101 is given to a quantization LUT 102 and a reduction circuit 105. The quantization LUT 102 converts e.g. 8-bit data into 4-bit data. The reduction circuit 105 sums all pixel values in e.g. 3×3 blocks and divides the sum by 9 to convert the input image 101 into a reduced image whose longitudinal and lateral sizes are reduced 1/3 respectively. A 1st coder 103 encodes a quantization index quantized by the quantization LUT 102 into a 1st code 104. A 2nd coder 105 encodes the reduced image reduced by the reduction circuit 105 into a 2nd code 107.