IMAGE COMPRESSING DEVICE, IMAGE RESTORING DEVICE, AND PROGRAM

摘要

An original pixel data group composed of pixel data on continuous pixels in image data is orthogonally transformed. Coefficients indicating the frequency components are outputted while limiting the number of coefficients to a predetermined number from the lowest frequency side. The difference value between a coefficient and the previously restored one is calculated for each coefficient, and the coefficient difference value is quantized. The quantized value obtained by the quantization is dequantized. A predetermined number of coefficients are restored by calculation using the coefficient difference value obtained by the dequantization and the previously restored one to perform orthogonal inverse transformation, thus restoring the original pixel data group. For each pixel, the pixel difference value between the original pixel data group and the restored original pixel data group is calculated. The quantized value of the coefficient difference value and the pixel difference value are encoded, and the compressed data is outputted.