A method of signal-processing input image data of a display device including a plurality of pixels, each pixel including a green subpixel and one of a red subpixel and a blue subpixel, the method includes: performing a gamma-conversion on input image data corresponding to the one of the red subpixel and the blue subpixel in each pixel; distributing the gamma-converted input image data corresponding to a center pixel to image data of a pixel in a vertical direction based on the center pixel by a first ratio; and distributing the gamma-converted input image data corresponding to the center pixel to image data of a pixel in a horizontal direction based on the center pixel by a second ratio, where the green subpixel and the one of the red subpixel and the blue subpixel are diagonally disposed in each pixel.