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US 7,612,915 B2Granted
Determining composite grays
AssigneeHewlett-Packard Development Company, L.P.
InventorsHuanzhao Zeng, Mary Nielsen
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Abstract
A system and method for determining composite grays using device values. Device values are received from image data on which color separation was performed. Gray component replacement are determined on black point device values by using target lightness values, target chromaticity values, and target black device values. A printing device and a computer readable media having computer instructions for implementing the method of determining composite grays are also provided.
Claims19
A computer-readable medium having instructions stored thereon such that execution of the instructions by a processing device causes a method for determining composite grays to be performed, the method comprising:
- defining target lightness values by performing a black point adjustment on lightness values of black device values, where performing the black point adjustment comprises evaluating:
- Lcrv=Lcbp+(Linp−Lpbp)*(Lwp−Lcbp)/(Lwp−Lpbp),
- where Lcrv is a target lightness value being defined, Lcbp is a lightness value of a composite gray black point for a device, Linp is an input lightness value for a black device point, Lpbp is a lightness value of a process black point for the device, and Lwp is a lightness value of a media white point;
- defining target chromaticity values corresponding with a chromaticity curve of neutral grays;
- defining target black device values by performing gray component replacement on black device values, where performing the gray component replacement comprises evaluating:
- Kgcr=Kmax*((Kinp−Kstr)/(UPPER−Kstr))^EF,
- where Kgcr is a linearized black device value being defined and having a replaced gray component, Kmax is an upper black device value for the device, Kinp is an input linearized black device value having a gray component to be replaced, Kstr is a starting value for gray component replacement, UPPER is an upper device value for the device, and EF is an exponential shaping factor;
- and
- determining composite gray device values by using the target lightness values, the target chromaticity values, and the target black device values.
6 more elements
A computer readable medium, having instructions stored thereon for
- causing a device to perform a method, comprising:
- sampling black device values to obtain linearized black device values;
- calculating lightness values of the linearized black device values, by evaluating:
- Lcrv=Lcbp+(Linp−Lpbp)*(Lwp−Lcbp)/(Lwp−Lpbp),
- where Lcrv is a target lightness value being calculated, Lcbp is a lightness value of a composite gray black point for a device, Linp is an input lightness value for a black device point, Lpbp is a lightness value of a process black point for the device, and Lwp is a lightness value of a media white point;
- digitizing the linearized black device values to form digitized black device values;
- determining black device values for composite gray device values by performing a gray component replacement on the digitized black device values, where performing the gray component replacement comprises evaluating:
- Kgcr=Kmax*(Kinp−Kstr)/(UPPER−Kstr))^EF,
- where Kgcr is a linearized black device value being determined and having a replaced gray component, Kmax is an upper black device value for the device, Kinp is an input linearized black device value having a gray component to be replaced, Kstr is a starting value for gray component replacement, UPPER is an upper device value for the device, and EF is an exponential shaping factor;
- and
- determining lightness values of the non-black device values of the composite gray device values by using the calculated lightness values.
8 more elements
A printing device, comprising:
- a processor;
- a memory coupled to the processor;
- and
- an ASIC, the ASIC including instructions executable to:
- generate a conversion look-up-table that relates device values of a device to color exchange space values;
- generate a digital-to-linear look-up-table for black device values of the device;
- sample a black device value from the digital-to-linear look-up table and by employing gray component replacement, where performing the gray component replacement comprises evaluating:
- Kgcr=Kmax*((Kinp−Kstr)/(UPPER−KstrY))^EF,
- where Kgcr is a linearized black device value being defined and having a replaced gray component, Kmax is an upper black device value for the device, Kinp is an input linearized black device value having a gray component to be replaced, Kstr is a starting value for gray component replacement, UPPER is an upper device value for the device, and EF is an exponential shaping factor;
- and
- determine at least a portion of a composite gray color for the output device by using the sampled black device value.
8 more elements
A device, comprising:
- a processor;
- a memory coupled to the processor;
- and
- means for generating balanced composite grays suitable for mapping to a device gamut without adjusting a neutral balance of the grays, by performing color matching during a color separation process wherein the means for generating includes instructions executable to generate the balanced composite gray components by at least performing gray component replacement, where performing the gray component replacement comprises evaluating
- Kgcr=Kmax*((Kinp−Kstr)/(UPPER−Kstr))^EF,
- where Kgcr is a linearized black device value being defined and having a replaced gray component, Kmax is an upper black device value for the device, Kinp is an input linearized black device value having a gray component to be replaced, Kstr is a starting value for gray component replacement, UPPER is an upper device value for the device, and EF is an exponential shaping factor.
3 more elements
Dependencies are inferred from the claim text.