IMAGE COMPRESSOR

In an image compressor, a color space converting unit separates an image data into a luminance data and a chrominance data. An image block-dividing unit block-divides each of the luminance and chrominance data separated by the color space converting unit into a plurality of blocks each of which includes adjacent pixels. A luminance threshold value determining unit determines a threshold value for binarizing the luminance data. A luminance binarizing unit binarizes the luminance data using the determined threshold value. A typical value forming unit forms two typical values for each of the block-divided luminance and chrominance data in accordance with the luminance data. A binarized luminance compressing unit encodes the binarized luminance data using dictionaries whose number is smaller than the number of all combinations of the luminance data.