Algorithms for coding scanned halftone pictures
A method for coding scanned documents containing halftone pictures, e.g. newspapers and magazines, for transmission purposes is proposed. The halftone screen is estimated and the grey value of each dot is found, thus giving a compact description. At the receiver the picture is rescreened. A novel data structure and related algorithms for handling the digital screen without restrictions on the screen parameters is presented. Data compression rates above 20 are obtained for the halftone pictures. The algorithms are suited for implementation with fast dedicated hardware. The rescreening can also be used as digital halftoning with arbitrary screens, using lookup tables.<<ETX>>