1. A method for processing original image signals of an image composed of a plurality of pixels, said method comprising the steps of: converting said image in respect to said original image signals; extracting image features for every pixel included in said plurality of pixels in respect to said original image signals; and performing a frequency processing operation for compensating for a sharpness level of said image, based on said image features extracted in said extracting step, so as to reduce a variation of said sharpness level before and after said converting step.