A method for scaling up an image in a display device includes acquiring luminance data and color data of a plurality of pixels in the image; generating high frequency components according to the luminance data of a first pixel and a plurality of second pixels adjacent to the first pixel in each set of adjacent pixels among the plurality of pixels; adjusting the high frequency components corresponding to each set of adjacent pixels, for making a sum of the high frequency components corresponding to each set of adjacent pixels to be within a predetermined range; and transforming the luminance data of the first pixel, the high frequency components and duplicating the color data of the first pixel in each set of adjacent pixels, to generate image data of a plurality of scaling-up points between the first pixel and each of plurality of second pixels in each set of adjacent pixels.