In enlarging an image by a super-resolution process using learned data, a reference value obtained from each patch and the pixel values of peripheral pixels in the patch are compared to generate binary or ternary comparison codes, and a patch of a high-resolution component corresponding to a binary pattern code or a ternary pattern code generated from the comparison codes is read. When a high-frequency component is contained the binary pattern code may be used; otherwise the ternary pattern code may be used. It is possible to reduce the storage capacity of the coefficient data storage unit and to improve the sense of high resolution.