Digital multitoning with overmodulation for smooth texture transition

Multilevel halftoning (multitoning) is an extension of bitonal halftoning, in which the appearance of intermediate tones is created by the spatial mod ulation of more than two tones, i.e., black, white, and one or more shades of gray. in this paper, the conventional multitoning approach and a previou sly proposed approach, both using stochastic screen dithering, are investig ated. A human visual model is employed to measure the perceived halftone er ror for both algorithms. The performance of each algorithm at gray levels n ear the printer's intermediate output levels is compared. Based on this stu dy, a new overmodulation algorithm is proposed. The multitone output is mea n preserving with respect to the input and the new algorithm requires littl e additional computation. It will be shown that, with this simple overmodul ation scheme, we will be able to manipulate the dot patterns around the int ermediate output levels to achieve desired halftone patterns. implementatio n issues related to optimal output level selection and inkjet-printing simu lation for this new scheme will also be reported. (C) 1999 SPIE and IS&T. [ S1017-9909(99)00203-2].