1. A method of processing an input image to obtain an output image, the input image being formed from input pixels having brightness levels, the method comprising the steps of: (a) detecting pixel-to-pixel variations in the brightness levels in at least one direction in the input image, thereby generating high spatial frequency information; (b) setting interpolation points with spacing varying according to the high spatial frequency information, and (c) generating output pixels from the input pixels by interpolation at the interpolation points.