1. An image processing method for adjusting a luminance value of each pixel included in an input image, the image processing method comprising the steps of: (S 4 ) demarcating a closed region β(x, y) made up of a plurality of pixels in the input image as a target region, moving the target region within the input image by predetermined pixel units to respectively calculate a maximum value and a minimum value of luminance energy defined as a luminance arrangement in the target region, and calculating difference data of the luminance energy; and (S 6 ) adapting the difference data to the input image in order to generate an output image.