An image processing apparatus inputs an image and then reads out, from a memory, to perform image processing for an image of a second region of the input image, an image of a region superimposed on the second region, and an image of a part of a first region adjacent to the second region, and controls a position of padding, wherein the padding results from image reduction of the first region, performed before the image processing for the image of the second region, so that the padding that results from the image reduction of the first region is not read out for the image processing for the image of the second region.