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US 5,297,058 AGranted
Method for creating multicolored halftone reproductions from continuous tone monochrome originals
AssigneeE. I. Du Pont de Nemours and Company
InventorMark R. Samworth
Life of this patent
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Abstract
A method for generating halftone images from monochrome original images and, more particularly, to a method for reproducing a monochrome original image using at least two different colorants to create an image having a preselected hue and chroma while substantially maintaining the same lightness as in the monochrome original image.
Claims11
A method for producing a multi-colorant output image from an input monochrome image having a lightness, the multi-colorant output image having a preselected chroma, a preselected hue and a desired lightness comprising:
- (a) selecting a first transfer function correlating optical density values (Do) of the monochrome input image to percent dot areas (% Dt) of the multi-colorant output image such that use of the first transfer function produces a first single colorant image having the desired Lightness;
- (b) selecting a sample image from a set of sample images, each of the sample images having a chroma, a hue and a lightness, the lightness being the same or substantially the same in each of the sample images, each of the sample images generated using a combination of at least two colorants;
- (c) establishing a colorant transfer function for each of the colorants such that use of each of the colorant transfer functions produces a single colorant output image such that the multi-colorant output image comprises the combination of all of the single colorant output images generated from the colorant transfer functions where the multi-colorant output image has a lightness equal to or substantially equal to the lightness of the first single colorant image generated using the first transfer function and the same or substantially the same hue and chroma of the selected sample image, wherein the colorant transfer functions are established using an equation where A.sub.C is a function of A and W.sub.C and is independent of gray level (D.sub.o) where:
- A.sub.c is a percent dot area for a given lightness value corresponding to the colorant transfer function for a colorant,
- A is a percent dot area for the same lightness value calculated based on the first transfer function, and
- W.sub.c is a color weight factor derived for each of the colorants for each of the sample images;
- and
- (d) using the colorant transfer functions to generate the multi-colorant output image.
5 more elements
Dependencies are inferred from the claim text.