ABSTRACT: In this paper, we introduce the concept of green-noise--the mid-frequency component of white noise--and its advantages over blue-noise for 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-gain. Error-diffusion with output dependent feedback and variations based on filter weight perturbation are shown to be good generators of green-noise, allowing for tunable coarseness. Using statistics developed for blue-noise, we closely examine the spectral content of resulting dither patterns; furthermore, two spatial domain statistics for analyzing the spatial arrangement of pixels in aperiodic dither patterns are introduced because green-noise patterns may be anisotropic and therefore spectral statistics based on radial averages may be inappropriate for their study.
APPEARED: Proceedings of the IEEE, vol. 86, no. 12, pp. 2424-2442, Dec 1998.
SPONSORS: This work was sponsored, in part, by the National Science Foundation under grant CDA-9703088