In at least one embodiment of the present invention, quality of image is improved by sufficiently sharpening the image through an appropriate high-frequency compensation with a simple arrangement, not only for still images but also for moving images and even if the images have already undergone image enlarging processes. In at least one embodiment, an HPF extracts high-frequency components from an input image signal. A square operator generates a squared signal by squaring the first signal. A first differentiator generates a first differentiation signal by differentiating the squared signal. The second differentiator generates a second differentiation signal by differentiating the input image signal. A multiplier generates a second signal by multiplying the first differentiation signal by the second differentiation signal. An adder generates an output image signal by adding the second signal to the input image signal, as a compensation signal.