Direct Pattern Control Halftoning of Neugebauer Primaries

Abstract

Halftoning is a key stage of any printing image processing pipeline. With colorant-channel approaches, a key challenge for matrix-based halftoning is the co-optimization of the matrices used for individual colorants, which becomes increasingly complex and over-constrained as the number of colorants increases. Both choices of screen angles (in clustered-dot cases) or structures, and control over how individual matrices relate to each other and result in over-versus side-by-side printing of the colorants, impose challenging restrictions. The solution presented in this paper relies on the benefits of a halftone area Neugebauer separation pipeline, where local Neugebauer Primary use is specified at each pixel and where halftoning can be performed using a single matrix, regardless of the number of colorants. The provably complete plane dependence of the resulting halftones will be presented among the solution's benefits.

Maximizing Neugebauer Primary Control: Beyond Halftoning

“…Once a mapping from input color to NPac is defined, the role of halftoning is then only that of spatially distributing the NPac according to the NP probabilities it dictates, without the ability to introduce new NPs or alter those defined at the input NPac. While several halftoning approaches are possible, such as device state error diffusion [6] based processes, it has been shown previously that a careful choice of pattern encoded in a tileable selector-value array used in the Parallel Random Area Weighted Coverage Selection (PARAWACS) approach results in the highest levels of IQ as well as deterministic pattern control and additional benefits [7]. There, the focus was on the goodness of pattern design to generate the highest levels of IQ, the property of pattern determinism has not been exploited so far and turns out to be a key enabler for extending print control beyond the halftone image.…”