1. An image processing apparatus comprising: an input device via which an image is input; and a processor configured to detect an edge of the image by applying at least one directional filter that is alignable in a direction with respect to the image, to calculate a mean value of a plurality of pixel values of a plurality of pixels that correspond to the edge, to determine a correction value that corresponds to each pixel of the image based on the calculated mean value, and to apply the determined correction value to the image in order to correct the image, wherein the processor is further configured to determine the correction value as varying inversely with respect to the calculated mean value such that the correction value is determined to be smaller when the calculated mean value is greater, and the correction value is determined to be greater when the calculated mean value is smaller.