Relation between grayvalue and noise frequencies in two- and three-level digital halftoning

In digital halftoning a close relationship exists between the local grayval ues in the input image and the spatial frequencies of the quantization nois e of the quantized image. Halftoning algorithms usually reproduce low frequ encies well by introducing quantization noise of higher frequencies. We pre sent and discuss a simple model for the relationship between grayvalue and quantization noise frequencies. Optimization experiments with two and three quantization levels are presented. (C) 1999 Elsevier Science B.V. All righ ts reserved.