Method for halftoning using interlocked threshold arrays or interlocked dot profiles

The present invention relates generally to a method for halftoning digital color images and is particularly directed to the use of interlocked threshold arrays or interlocked dot profiles. The invention is specifically disclosed in which images are rendered using a dither matrix representing correla...

Ausführliche Beschreibung

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Bibliographische Detailangaben
Hauptverfasser: Cooper, Brian Edward, Love, Shaun Timothy
Format: Patent
Sprache:eng
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Beschreibung
Zusammenfassung:The present invention relates generally to a method for halftoning digital color images and is particularly directed to the use of interlocked threshold arrays or interlocked dot profiles. The invention is specifically disclosed in which images are rendered using a dither matrix representing correlated dot patterns, where the dots of each dot pattern are arranged to minimize a function of the variances in the number of dots per region across an appropriate range of region sizes, and in which each color plane threshold array is generated while considering the threshold arrays for all of the other color planes so as to become interlocked; or in which multiple threshold arrays are generated for a single color plane, but while each of these threshold arrays is generated, the other arrays for that color plane are considered so as to become interlocked. A dispersed-dot stochastic dither array is provided for rendering halftone images having excellent visual quality. For color printing, a separate threshold array is generated for each of the color planes, however, the stochastic screens are interlocked so that the threshold arrays are generated while considering the other color threshold arrays. In this manner, a blue noise distribution may be produced by the individual arrays as well as by any combination of the individual arrays. When generating a single threshold array for a color plane, a particular criterion is used to determine where the next threshold value should be located, and the selection of a threshold location in each array considers the criterion for all the threshold arrays being generated. By using the interlocked threshold arrays approach, the overall visual affect will be improved for both individual threshold arrays and for a combination of more than one of the threshold arrays. The present invention also is used to generating a set of interlocked dot profiles which do not use a threshold array for halftoning. In an opposite sense, the interlocked threshold arrays can be generated without using dot profiles during the formative steps of the threshold array. More than one threshold array could be generated in this manner, and these threshold arrays could also be interlocked with respect to one another. Other alternative methodologies include globally optimizing interlocked threshold arrays by simultaneously considering all tone levels for all threshold arrays being generated to avoid locally suboptimal solutions; or regional optimization can be