Inverse ordered dithered halftoning using permutation filters

The problem of reconstructing a continuous-tone image given its ordered dithered halftone image is considered. We utilize a modular class of non-linear filters, denoted as binary permutation filters, which can reconstruct the continuous-tone information as well as image details which provide important visual cues. Binary permutation filters are based on the space-rank ordering of the halftone samples which is provided by the multiset permutation of the “on” pixels in a halftone observation window. By varying the space-rank order information utilized in the estimate, for a given window size, we obtain a wide range of filters. We present simulations showing that binary permutation filters are modular, robust to image source characteristics, and that their results produce high visual quality image reconstruction