A display device comprising: a calculator comprising calculating circuitry configured to calculate a number of horizontal pixels and a number of vertical pixels which are recognized as one pixel by a viewer through the display when the viewer watches the display with a viewer's eyesight at a viewing distance by using at least one of the viewing distance of the viewer, the viewer's eyesight, a resolution of the display, and a size of the display; a determiner comprising determining circuitry configured to divide pixels of an image into a plurality of pixel groups, the size of each pixel group being defined by the calculated number of horizontal pixels and the calculated number of vertical pixels, to determine a number of first pixels included in each pixel group and a number of second pixels included in each pixel group based on an average pixel value of some or all pixels included in the image, and to determine positions of the first and second pixels in each pixel group based on the determined number of first pixels and the determined number of second pixels in each pixel group; a first image processor configured to perform an image-enhancement process on the first pixels according to a first image enhancement factor at a first increase rate, wherein the first increase rate depends on the number of first pixels in the pixel group; a second image processor configured to perform an image-enhancement process on the second pixels according to a second image enhancement factor at a second increase rate, wherein the second increase rate depends on the number of second pixels in the pixel group; and a display configured to display the image to which the image-enhancement process has been applied by the first and second image processors (141; 142). a calculator comprising calculating circuitry configured to calculate a number of horizontal pixels and a number of vertical pixels which are recognized as one pixel by a viewer through the display when the viewer watches the display with a viewer's eyesight at a viewing distance by using at least one of the viewing distance of the viewer, the viewer's eyesight, a resolution of the display, and a size of the display; a determiner comprising determining circuitry configured to divide pixels of an image into a plurality of pixel groups, the size of each pixel group being defined by the calculated number of horizontal pixels and the calculated number of vertical pixels, to determine a number of first pixels included in each pixel group and a number of second pixels included in each pixel group based on an average pixel value of some or all pixels included in the image, and to determine positions of the first and second pixels in each pixel group based on the determined number of first pixels and the determined number of second pixels in each pixel group; a first image processor configured to perform an image-enhancement process on the first pixels according to a first image enhancement factor at a first increase rate, wherein the first increase rate depends on the number of first pixels in the pixel group; a second image processor configured to perform an image-enhancement process on the second pixels according to a second image enhancement factor at a second increase rate, wherein the second increase rate depends on the number of second pixels in the pixel group; and a display configured to display the image to which the image-enhancement process has been applied by the first and second image processors (141; 142).