Abstract: When a display image is a photographic image or a moving image, an ON signal is inputted from the ON-OFF circuit and the ON-OFF circuit to the sharpness circuit and the gamma correction circuit under a control signal from the control circuit. An inputted image signal Fc is subjected to sharpness processing for edge enhancement by the sharpness circuit, and the intermediate signal level of the image signal Fc is raised by gamma correction of the gamma correction circuit. Thus, the CRT can display a sharp, high-quality photographic or moving image having an enhanced edge and emitting light with its luminance proportional to the signal level. When a display image is a code display image of letters or the like, the sharpness circuit is controlled to be in an unactivated state and the gamma correction circuit is controlled to be in an activated state under a control signal from the control circuit.