US6345117B2
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for automatic trap selection for correcting for separation misregistration in color printing
Assignee: Xerox Corp
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Filing: 2001-05-29
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Granted: 2002-02-05
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Expires: 2021-05-29
Abstract
Abstract A color printing systems which deposits colors on a separation by separation basis is calibrated to determine a printed color responsive to a requested color, based on a mapping of device independent colors to printer output colors. The system provides trapping to correct misregistration between printer output colors due to imperfect placement of said separation color. Such a system includes calibration data stored in a device memory mapping a set of device independent colors to printer output colors; a trapping processor, using calibration data to determine device independent colors for printer colors. Also included is a trapping calculation processor, converting device independent colors to a color space in which equivalent color differences in human color perception are approximately equivalent values, determining whether to trap, a trap color, and a trapping location for the trapping color. An image modification processor is also provided to alter the image accordance with any determinations of said trapping calculation processor
Inventors
- 👤 R. Victor Klassen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 18:28
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/56; H04N1/58
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
319 words
A method for optimizing rap selection for correcting for separation misregistration in color printing of a color image having at least two input colors (C 1 ,C 2 ), a) generating a list of all unique colors appearing between colors (C 1 ) and (C 2 ) by processing all possible substitutions of a separation in color (C 1 ) with a separation in color (C 2 ); b) sorting said list into an array of vectors considering two separations equal if they differ by less than a predetermined tolerance with an integer value assigned to each of said colors in said array thereby forming for each array entry an associated CMYK(C 1 ,C 2 ) color; c) converting each element in said array of CMYK(C 1 ,C 2 ) colors from device coordinates into LAB-Vectors of device dependent color space each representing a list of possible misregistration of colors (C 1 ,C 2 ) in LAB-space; d) constructing a visibility vector(C 1 ,C 2 ) for each input color (C 1 ,C 2 ) and for each element in said LAB-Vector computing a difference value from color (C 1 ) and from color (C 2 ) for that element and storing the minimum of these two differences corresponding to the visibilities of all of said misregistration colors; e) for each entry in said visibility vector, if a maximum entry in said visibility vector is less than a threshold ‘t’ then the corresponding misregistration will not be visible and no action need be taken at (C 1 , C 2 ) otherwise if the maximum is greater than threshold ‘t’ a candidate color for trapping is selected from a predetermined set of trapping colors maintained as a palette; and f) determining if the visibility of said candidate color for trapping is worse than the initial misregistration visibility of step (d), and if so, then no trapping color is selected.
Claim 2
Independent Claim
319 words
A method for optimizing rap selection for correcting for separation misregistration in color printing of a color image having at least two input colors (C 1 ,C 2 ), a) generating a list of all unique colors appearing between colors (C 1 ) and (C 2 ) by processing all possible substitutions of a separation in color (C 1 ) with a separation in color (C 2 ); b) sorting said list into an array of vectors considering two separations equal if they differ by less than a predetermined tolerance with an integer value assigned to each of said colors in said array thereby forming for each array entry an associated CMYK(C 1 ,C 2 ) color; c) converting each element in said array of CMYK(C 1 ,C 2 ) colors from device coordinates into LAB-Vectors of device dependent color space each representing a list of possible misregistration of colors (C 1 ,C 2 ) in LAB-space; d) constructing a visibility vector(C 1 ,C 2 ) for each input color (C 1 ,C 2 ) and for each element in said LAB-Vector computing a difference value from color (C 1 ) and from color (C 2 ) for that element and storing the minimum of these two differences corresponding to the visibilities of all of said misregistration colors; e) for each entry in said visibility vector, if a maximum entry in said visibility vector is less than a threshold ‘t’ then the corresponding misregistration will not be visible and no action need be taken at (C 1 , C 2 ) otherwise if the maximum is greater than threshold ‘t’ a candidate color for trapping is selected from a predetermined set of trapping colors maintained as a palette; and f) determining if the visibility of said candidate color for trapping is worse than the initial misregistration visibility of step (d), and if so, then no trapping color is selected.
Claim 3
Dependent Claim
32 words
As in claim 1 , wherein said LAB-Vectors are constructed from device dependent color CMYK-Vectors generated from samples of CMYK colors from said device, organized into a table and mapped to LAB-Space.
Claim 4
Dependent Claim
71 words
As in claim 2 , wherein said LAB-Space is one of CIE-LAB space of CIE-LUV Space in order to take advantage of the correlation to visually perceptible color differences which allow said colors to be used to determine whether any specific color is likely to be visually perceptible, irrespective of the misregistration color; said visibility correlation usable as a metric as to how apparent a trap of trap modification can be.
Claim 5
Dependent Claim
151 words
As in claim 1 wherein said step of choosing a color to insert between (C 1 ) and (C 2 ), comparing every color ‘T’ in said color palette to CMYK(C 1 ,C 2 ) color and if ‘T’ is NOT between (C 1 ,C 2 ) then discarding ‘K’, and if ‘T’ is between (C 1 ,C 2 ) then, for each color ‘T’ for which CMY are between (C 1 ,C 2 ) generating a Trap-Visibility-Vector ‘T a ’ and a Trap-Visibility-Vector ‘T b ’ and determining therebetween a max visibility value ‘t- max ’ in ‘T a , and ‘T b ’ to produce a visibility of T’ against color (C 1 ) or color (C 2 ) with the lowest maximum visibility ‘T min ’ of all colors between (C 1 ) and (C 2 ) being representative of the best trapping color candidate to be selected.
Claim 6
Dependent Claim
46 words
As in claim 4 , if it is determined that the visibility of said candidate trapping color is NOT worse than the initial misregistration visibility of step (f), then choosing the candidate color ‘T’ whose worst visibility is the best of all the candidate trapping colors.
Claim 7
Dependent Claim
51 words
As in claim 4 , if it is determined that the visibility of said candidate trapping color is NOT worse than the initial misregistration visibility of step (f), then taking the sum of the squares of the visibilities over all misregistrations and choosing the candidate trapping color with the smallest sum.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2005-02-04 | 2005-08-06 | 2006-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2009-02-04 | 2009-08-06 | 2010-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2013-02-04 | 2013-08-06 | 2014-02-05 | $7700.00 | Window Closed / Lapsed |