Stochastic Clustered-Dot Dithering

V. Ostromoukhov, R.D. Hersch

Conf. Color Imaging: Device-Independent Color, Color Hardcopy, and Graphic Arts IV, SPIE Vol. 3648, 1999, pp. 496-505

A new technique for building stochastic clustered-dot screens is being proposed. A large dither matrix comprising thousands of stochastically laid out screen dots is constructed by first laying out the screen dot centers. Screen dot centers are obtained by placing discrete disks of a chosen radius at free cell locations when traversing the dither array cells according to either a discretely rotated Hilbert space-filling curve or a random space-filling curve. After Delauney triangulation of the screen dot centers, the maximal surface of each screen dot is computed and iso-inten- sity regions are created. This iso-intensity map is converted to an anti-aliased grayscale image, i.e. to an array of preliminary threshold values. These threshold values are renumbered to obtain the threshold values of the final dither threshold array. By changing the disk radius, the screen dot size can be adapted to the characteristics of particular printing devices. Larger screen dots may improve the tone reproduction of printers having important dot gain.

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