To enlarge an image in vertical and horizontal directions with favorable image quality while reducing jaggy feeling for a diagonal line.

An image processing apparatus for providing enlargement processing with diagonal line processing by executing interpolation processing using a pixel-pair correlation on the diagonal line contained in an input image includes an output pixel location determination part 101 for determining an output pixel location, i.e., a location of the pixel contained in an enlarged image, an m×n pixels extraction part 102 for extracting a set of a given number of input pixels around the output pixels locations, a vertical direction enlarging part with diagonal line processing 301 for executing enlargement processing with diagonal line processing in a vertical direction on the basis of the output pixel location and the set of a given number of input pixels, and a horizontal direction enlarging part with diagonal line processing 302 for executing enlargement processing with diagonal line processing in a horizontal direction on the basis of the output pixel location, the set of the given number of input pixels, and an enlargement processing result by the vertical direction enlarging part with diagonal line processing 301.

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