Halftoning for hi-fi color inks
AssigneeXerox Corporation
InventorsDavid A. Mantell, Thyagarajan Balasubramanian
Life of this patent
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Abstract
In a hi-fi color printing system, an inverted halftone screen is provided having the same angle and frequency as a halftone screen for an opposing color. The dots of the inverse halftone screen are configured to be located midway between the centers of the dots of the half-tone screen. The halftone screen and inverted halftone screen are used in the printing process to extend the gamut of colors within a printing system, render improved neutral colors, and provide an improved transition through neutral regions of color space. The present invention allows for additional printing of multiple colors without the need for increasing the number of screens used in the image processing system.
Claims19
A digital printing apparatus configured to print an image having at least two different colors, comprising:
- a first halftone screen, having a plurality of pixels, associated with a first of a plurality of colorants including cyan, magenta, yellow, or black;
- and
- a second halftone screen associated with a second colorant, which is different than any of the first colorants, having a plurality of pixels, the pixels of the first halftone screen not overlapping the pixels of the second halftone screen when the sum of the two colorants is less than or equal to 100% coverage.
In a printing apparatus capable of printing a plurality of colorants, a method of simultaneously printing a first colorant and a second colorant of the same or opposite hues, comprising the steps of:
- forming a first halftone screen having a plurality of pixels of the first colorant;
- determining a constraint that limits the sum of the two colorants to be always less than or equal to 100% coverage;
- forming a second halftone screen having a plurality of pixels of the second colorant, wherein the pixels of the second halftone screen do not overlap with the pixels of the first halftone screen as long as the constraint is satisfied;
- and
- printing the colorant associated with the first halftone screen and the colorant associated with the second halftone screen.
In a printing apparatus capable of printing a plurality of colorants, a method of simultaneously printing a first colorant and a second colorant of a same or an opposite hue of the first colorant, comprising the steps of:
- forming a first halftone screen having a plurality of pixels of the first colorant;
- positioning the first halftone screen at a first angle;
- determining a constraint that limits the sum of the two colorants to be always less than or equal to 100% coverage;
- forming a second halftone screen having a plurality of pixels of the second colorant, which are at the first halftone screen angle, wherein the pixels of the second halftone screen do not overlap with the pixels of the first halftone screen as long as the constraint is satisfied;
- and
- printing the color associated with the first halftone screen and the colorant associated with the second halftone screen.
Dependencies are inferred from the claim text.