Provided is a method of converting relative luminance data of a picture frame into relative luminance data of a display panel. The picture frame includes a region composed of a plurality of frame unit regions arranged in a matrix. The frame unit region is composed of six pixels. The display area of the display panel includes a region composed of a plurality of panel unit areas arranged in a matrix. The panel unit area is composed of twelve sub-pixels arranged in a delta-nabla position. The relative luminance value of each pixel is assigned to one or two subpixels of each of the three color subpixels. The relative luminance value of each subpixel is determined from the relative luminance value of the corresponding two adjacent pixels.