1. An image processing method for processing images in a plurality of related frames, in which the image data supplied from an image data source is subjected to specified image processing so as to produce output image data, comprising the steps of: in the processing of an image in a first frame among the plurality of related frames, designating a specific region in the first frame; calculating an image characteristic quantity of the specific region; and subjecting the specific region to image modification; as well as storing information about the image characteristic quantity of the specific region and the image modification of specific region; and, further comprising the steps of: in the processing of the images in second and subsequent frames, extracting a similar region that is similar in said image characteristic quantity to the specific region without the image modification in said first frame; and subjecting the similar region to the same image modification as has been performed on the specific region of said first frame.