An apparatus determines a second pixel range of an uncorrected image necessary to generate a first pixel range having pixels in a preset range of a corrected image, including a cache unit determining the second pixel range and reading and holding the second pixel range from memory before executing correction. Correspondences indicating positions of the uncorrected image corresponding to positions of pixels of the corrected image, respectively, are preset. The cache unit specifies a position of the uncorrected image corresponding to a pixel of one of four corners of a rectangular third pixel range including the first pixel range based on the correspondence, specifies pixel ranges of the uncorrected image necessary for pixel value generation, respectively, at the four corners of the third pixel range based on the specified position, and determines a pixel range including a convex set including the specified pixel ranges as the second pixel range.