1. A display processor system for reproducing an image in a set of more than two greyscale steps comprising: a plurality of superpixels each including a number of pixels for providing an output representative of an incident image portion; means for providing a set of threshold levels for each pixel in a superpixel, which set is different from each of the sets of threshold levels of the other pixels in that superpixel and different from the set of greyscale steps; means for identifying the position of a given pixel in a superpixel and designating the particular set of threshold levels corresponding to the position of that given pixel; means for comparing the output of the given pixel with said particular set of threshold levels; and means, responsive to said means for comparing, for indicating a greyscale step in said set of more than two greyscale steps in response to an output from said given pixel equal to or in excess of at least one of said threshold levels in the set of threshold levels corresponding to that pixel position.