Color separation table optimized for a printing process according to a print attribute by selecting particular Neugebauer primaries and Neugebauer primary area coverages

Patent metadata

Field	Value
Publication number	US-9584700-B2
Application number	US-60549909-A
Country	US
Kind code	B2
Filing date	Oct 26, 2009
Priority date	Oct 26, 2009
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

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.

First claim

What is claimed is:

1. 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.

2. A method as recited in claim 1 comprising incorporating the second NPacs and corresponding color values directly into the color separation table.

3. A method as recited in claim 2 , further comprising replacing an optimized NPac linked to a certain color value by a second NPac linked to an approximately corresponding color value.

4. A method as recited in claim 1 , wherein the at least one pre-determined pair of halftone data and corresponding color value is included in a chart with colored patches.

5. 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.

6. A system as recited in claim 5 wherein the color separation table excludes the excluded NPs and at least one of the hull NPacs is a combination of at least one included NP and at least one excluded NP.

7. 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.

8. A method as recited in claim 7 wherein said generating is so that said color separation table includes NPacs not resulting from said computing that were determined to be optimized for producing certain colors on said print system.

9. A computer-program product comprising non-transitory computer-readable media encoded with code that, when executed by a processor, causes the processor to implement the method of claim 8 .

10. A method as recited in claim 7 including computing combination NPacs for colors not directly represented in said color separation table as linear combinations of said included NPs and said proxy NPacs.

11. A computer-program product comprising non-transitory computer-readable media encoded with code that, when executed by a processor, causes the processor to implement the method of claim 10 .

12. A computer-program product comprising non-transitory computer-readable media encoded with code that, when executed by a processor, causes the processor to implement the method of claim 7 .

13. 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

Assignees

• Morovic Jan
• Morovic Peter
• Benedicto Jordi Arnabat
• Vilar Jordi
• Hewlett Packard Development Co Lp

Inventors

• Morovic Jan
• Morovic Peter
• Benedicto Jordi Arnabat
• Vilar Jordi

Classifications

• H04N1/6061

  involving the consideration or construction of a gamut surface · CPC title

• H04N1/6058

  Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut · CPC title

• H04N1/6019

  using look-up tables (H04N1/6025 takes precedence) · CPC title

• H04N1/52 Primary

  Circuits or arrangements for halftone screening · CPC title

• H04N1/6069

  spatially varying within the image · CPC title