The present invention relates to a technique for correcting tones of a digitized image, for use in a mobile terminal or the like. The use of a conventional image tone correction technique to backlight correction imposes a limit on improvement in local contrast in a bright region or a dark region. According to the present invention, a block timing generation part (102) divides one image area into a plurality of blocks, an average luminance calculation part (103) calculates an average luminance level per block specified at the part 102, a correction-amount-per-block calculation part (104) calculates a direction of correction and a correction amount from an average luminance level per block, a correction-amount-per-pixel calculation part (105) interpolates the correction amount per block into the correction amount per pixel in that block, and a tone conversion part (107) reads out a final correction amount from a tone conversion table part (108), using the correction amount per pixel and luminance data of that pixel read out from a memory (106) as an address, to carry out tone conversion.