An apparatus includes an edge width detection circuit which detects an edge portion of image data and outputs an edge width of the detected edge portion, a ratio control amount generation circuit which generates a ration control amount in accordance with the edge width, a ratio generation circuit which generates a conversion ratio in accordance with the ratio control amount, and a pixel number conversion circuit which performs a conversion of pixel number of the image data using the conversion ratio, thereby enhancing sharpness of the edge portion in proper quantities.