Color separation table optimized for a printing process according to a print attribute by selecting particular Neugebauer primaries and Neugebauer primary area coverages
AssigneeHewlett-Packard Development Company, L.P.
InventorsJan Morovic, Peter Morovic, Jordi Arnabat Benedicto, Jordi Vilar
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Abstract
Method of setting up a color separation table for a specific print system, comprising finding first NP (Neugebauer Primary) area coverages of a specific print system that correspond to color values, adding second NP area coverages by converting halftone data from at least one pre-determined pair of halftone data and corresponding color value to NP area coverages, and generating a color separation table arranged as input for a halftone process that comprises color values linked to the corresponding first and second NP area coverages.
Claims16
A method of setting up a color separation table for a specific print system, the method comprising:
- finding first NPacs (Neugebauer Primary Area Coverages) of a specific print system that correspond to color values, at least one of the NPacs including contributions from plural NPs (Neugebauer Primaries), wherein the finding of first NPacs includes
- determining a print attribute value range pertaining to a reference print attribute value, and
- selecting base NPacs, including NPacs representing single NPs and combined NPs, that have print attribute values in the print attribute value range;
- obtaining second NP area coverages by converting halftone data from at least one pre-determined pair of halftone data and corresponding color value to NPacs, the halftone data including halftone patterns associated with colors;
- generating, by a computer, a color separation table arranged as input for a halftone process that includes color values linked to the corresponding at least some of the first and at least some of the second NPacs;
- including the second NPacs with the first NPacs to constitute base NPacs;
- selecting the base NPacs that are closest to the reference print attribute value for a corresponding color value;
- optimizing NPacs by computing linear combinations of the base NPacs, wherein the computing of linear combinations of the base NPacs includes,
- computing a convex hull of colors measured from patches in a predetermined color space,
- determining the NPacs corresponding to the colors forming the convex hull,
- comparing a weighted print attribute value of a linear combination of base NPacs on the convex hull to a print attribute value of a base NPac inside the convex hull having a corresponding color,
- keeping the base NPac inside the convex hull only if it has a print attribute value that is closer to the reference print attribute value than the weighted print attribute value of the linear combination of base NPacs on the convex hull, and
- assigning one of the base NPacs or the linear combination of base NPacs to a corresponding color value, depending on which is closest to the reference print attribute value.
A system comprising non-transitory media encoded with code defining a color-separation pipeline to convert colors to halftone patterns in a print system defining NPs (Neugebauer Primaries), the NPs including included NPs and excluded NPs, the pipeline including a color separation table associating colors with base NPacs (Neugebauer Primary Area Coverages) including single-NP (Neugebauer Primary) NPacs corresponding to said included NPs and multi-NP NPacs, said color separation table excluding said excluded NPs, at least one of the base NPacs being a linear combination of NPs including at least one excluded NP, the base NPacs being on of within a convex hull in a color space, the excluded NPs not being on or within the convex hull, the color-separation pipeline being to, when executed by a processor, convert colors not represented in the color-separation table as linear combinations of the base NPacs.
A method comprising:
- identifying, using a computer, included and excluded Neugebauer Primaries (NPs) of a print system, said included Neugebauer Primaries meeting a criterion, said excluded Neugebauer Primaries not meeting said criterion;
- computing, using said computer, proxy Neugebauer Primary Area Coverage Vectors (NPacs) meeting said criterion, each proxy NPac being a linear combination of NPs including at least one excluded NP and at least one included NP, the base NPacs being on of within a convex hull in a color space, the excluded NPs not being on or within the convex hull;
- and generating, using said computer, a color separation table excluding said excluded NPs and including at least one of said included NPs and at least one of said proxy NPacs.
A computer-program product comprising non-transitory media encoded with code that, when executed by a processor, causes the processor to implement a method including:
- finding first NPacs (Neugebauer Primary Area Coverages) of a specific print system that correspond to color values, at least one of the NPacs including contributions from plural NPs (Neugebauer Primaries), wherein the finding of first NPacs includes
- determining a print attribute value range pertaining to a reference print attribute value, and
- selecting base NPacs, including NPacs representing single NPs and combined NPs, that have print attribute values in the print attribute value range;
- obtaining second NP area coverages by converting halftone data from at least one pre-determined pair of halftone data and corresponding color value to NPacs, the halftone data including halftone patterns associated with colors;
- generating, by a computer, a color separation table arranged as input for a halftone process that includes color values linked to the corresponding at least some of the first and at least some of the second NPacs;
- including the second NPacs with the first NPacs to constitute base NPacs;
- selecting the base NPacs that are closest to the reference print attribute value for a corresponding color value;
- optimizing NPacs by computing linear combinations of the base NPacs, wherein the computing of linear combinations of the base NPacs includes,
- computing a convex hull of colors measured from patches in a predetermined color space,
- determining the NPacs corresponding to the colors forming the convex hull,
- comparing a weighted print attribute value of a linear combination of base NPacs on the convex hull to a print attribute value of a base NPac inside the convex hull having a corresponding color,
- keeping the base NPac inside the convex hull only if it has a print attribute value that is closer to the reference print attribute value than the weighted print attribute value of the linear combination of base NPacs on the convex hull, and
- assigning one of the base NPacs or the linear combination of base NPacs to a corresponding color value, depending on which is closest to the reference print attribute value.
Dependencies are inferred from the claim text.