Abstract: An image processing apparatus for image compression and decompression includes a smoothing part for smoothing image data of a reconstructed image by using a smoothing filter selected from among a plurality of smoothing filters having different smoothing effects, an averaging part for producing a set of values of averages of coefficients produced through discrete cosine transformation with respect to a plurality of blocks in the reconstructed image so that a distribution of the averages of the coefficients for a target block is generated, and a selection part for generating a signal to enable the smoothing part to select the smoothing filter by detecting whether or not peak values in the distribution of the averages of the coefficients, generated by the averaging part, appear substantially on a diagonal line of the target block passing a lowest-order position through a highest-order position of the target block.