US 5,861,896 A · Controlling ink migration and physical color gamut discontinuities in digital color printing

Abstract

In color graphics printing, incompatible inks, such as true black and color inks, tend to bleed across color field boundaries. Moreover, in four-color systems, there is a discontinuity in the physical color gamut, as distinguished from the logical color gamut, associated with the redundant color. A method is disclosed for alleviating both problems by adjusting image data prior to dithering. The method slightly shifts the logical color indicated in the image data so as to avoid the discontinuity that arises with neutral colors. Preferably, in a four-color printing system, yellow is depleted in the image data, so that after dithering, more dots of blue ink are printed in a given area than would be printed otherwise. For each pixel, the amount of correction is inversely related to the color saturation. The presence of blue ink dots within the substantially black field reduces bleed along the field edges.

Claims16

Dependent claims

A method for minimizing the physical color gamut discontinuity of an ink jet printer output formed by the application on a print media of a different density of redundant color ink dots at a preselected pixel location in place of primary color ink dots having equal data values, the method comprising:

(a) providing a print media on which a color image is to be printed;
(b) receiving color image data comprising a plurality of image data pixels, each of the plurality of image data pixels having a data value for each one of the primary colors;
(c) determining color saturation for each of the image data pixels from the color image data;
(d) adding adjustment color data to the color image data responsive to the determined saturation so that, for any given one of said image data pixels, less than all of the primary color data values are changed, to minimize the number of pixels having equal data values for each primary color so as to form adjusted image data representing an adjusted image, the adjusted image having minimized physical color gamut discontinuity;
and
(e) printing the adjusted image on the print media by applying primary color ink dots to the print media for each image data pixel having a density in accordance with the adjusted image data.

3 more elements

A method for minimizing color gamut discontinuity in an ink jet printer output, the method comprising:

providing a print medium on which to apply an image, said image formed of a plurality of pixel elements;
receiving first C, M and Y color image values for each of said pixel elements wherein at least one of said pixels has a grey component identified therewith formed by equal first C, M and Y values;
comparing said first C, M and Y color image values for each of said pixel elements to identify said at least one of said pixels having a grey component identified therewith formed by equal first C, M and Y values;
for each of said pixel elements having equal first C, M and Y values, adjusting a selected one but less than all of the first C, M and Y values to yield an adjusted value so that said adjusted value is different from said selected one of the first C, M and Y values;
and
applying a density of C, M and Y ink dots on said print medium for each of said pixel elements in response to said color image values and said adjusted value associated with each of said pixel elements.

3 more elements

Dependencies are inferred from the claim text.

Controlling ink migration and physical color gamut discontinuities in digital color printing

Life of this patent

Controlling ink migration and physical color gamut discontinuities in digital color printing

Life of this patent

Abstract

Claims16