Evaluation of green noise masks for electrophotographic halftoning

Green noise is the mid-frequency component of white noise and has been shown to have visually pleasing attributes when applied to digital halftoning. Unlike blue noise dither patterns, which are composed exclusively of isolated pixels, green noise dither patterns are composed of pixel-clusters making them less susceptible to image degradation from non-ideal printing artifacts such as dot-loss. Clearly, these patterns reduce the spatial variation in tone produced by electrophotographic printers when printing a constant shade of gray, but to date, no study has been presented showing the amount of reduction. In this paper, we address this problem by studying the effects of changing the average cluster size in a green noise dither pattern, measuring the resulting spatial variations for a Lexmark Optra laser printer in 1200 dpi mode. The print quality is evaluated in terms of the visibility of printer mechanism noise and the average change in tone across the printed page.