Membrane-based methods and system for color characterization
View Patent ↗Methods and systems are presented for characterizing a printer, display or other color reproduction device in which a forward color transform having a parametric surface forward color transform and a nonparametric residual forward color transform is updated by adapting the parametric surface forward color transform using an input adaptation data set and a measured adaptation data set, generating a prediction data set in the second color space using the adapted parametric surface forward color transform and the nonparametric residual forward color transform, generating a prediction error data set in the second color space using the input adaptation data set and the prediction data set, generating a membrane forward color transform using the prediction error data set, and updating the forward color transform using the adapted parametric and nonparametric forward color transforms.
1. A method of characterizing a color reproduction device, the method comprising:
providing a forward color transform for the device mapping color from a first color space associated with an internal color representation of the device to a second color space representing measurements of observed color values, the forward color transform including a parametric surface forward color transform and a nonparametric residual forward color transform;
producing a plurality of visible adaptation test images according to an input adaptation data set in the first color space using the device;
measuring the adaptation test images to generate a measured adaptation data set in the second color space; and
using at least one processor, adapting the parametric surface forward color transform using the input adaptation data set and the measured adaptation data set;
using the at least one processor, generating a prediction data set in the second color space using the adapted parametric surface forward color transform and the nonparametric residual forward color transform;
using the at least one processor, generating a prediction error data set in the second color space using the input adaptation data set and the prediction data set;
using the at least one processor, generating a membrane forward color transform using the prediction error data set; and
using the at least one processor, updating the forward color transform using the adapted parametric and nonparametric forward color transforms.
2. The method of claim 1 , wherein updating the forward color transform comprises updating the forward color transform using the parametric surface and membrane forward color transforms and the nonparametric forward color transform.
3. The method of claim 1 , wherein generating the device independent prediction data set comprises:
evaluating the parametric surface forward color transform for each point in the input adaptation data set;
evaluating the nonparametric residual forward color transform for each point in the input adaptation data set; and
summing the parametric and nonparametric transform evaluations for each point in the input adaptation data set to generate the prediction data set.
4. The method of claim 3 , wherein generating the prediction error data set comprises for each point in the input adaptation data set, subtracting the values of the prediction data set from the values of the measured adaptation data set.
5. The method of claim 4 , wherein generating the membrane forward color transform comprises fitting a continuous and smooth membrane surface to the prediction error data set.
6. The method of claim 5 , wherein updating the forward color transform comprises summing the parametric surface forward color transform with the nonparametric residual forward color transform and the membrane forward color transform.
7. The method of claim 5 , wherein the input adaptation data set is a C,M,Y,K data set, and wherein the measured adaptation data set is an L,a*,b* data set.
8. The method of claim 1 , wherein generating the prediction error data set comprises for each point in the input adaptation data set, subtracting the values of the prediction data set from the values of the measured adaptation data set.
9. The method of claim 1 , wherein generating the membrane forward color transform comprises fitting a smooth membrane surface to the prediction error data set.
10. The method of claim 1 , wherein updating the forward color transform comprises summing the parametric surface forward color transform with the nonparametric residual forward color transform and the membrane forward color transform.
11. The method of claim 1 , wherein the input adaptation data set is a C,M,Y,K data set, and wherein the measured data set is an L,a*,b* data set.
12. A color processing device, comprising:
a rendering system operative to produce a visible image according to input color data in a first color space;
a system controller operative to provide the input color data to the rendering system according to a print job;
a sensor operative to generate measured data in a second color space representative of the visible image; and
a characterization system coupled with the system controller and the sensor, the characterization system comprising a forward color transform for the device mapping color from a first color space associated with an internal color representation of the device to a second color space representing measurements of observed color values, the forward color transform including a parametric surface forward color transform and a nonparametric residual forward color transform, the characterization system being operative to adapt the parametric surface forward color transform using an input adaptation data set of the first color space and a measured adaptation data set of the second color space, to generate a prediction data set in the second color space using the adapted parametric surface forward color transform and the nonparametric residual forward color transform, to generate a prediction error data set in the second color space using the input adaptation data set and the prediction data set, to generate a membrane forward color transform using the prediction error data set, and to update the forward color transform using the adapted parametric and nonparametric forward color transforms.
13. The color processing system of claim 12 , wherein the characterization system is operative to evaluate the parametric surface forward color transform for each point in the input adaptation data set, to evaluate the nonparametric residual forward color transform for each point in the input adaptation data set, and to sum the parametric and nonparametric transform evaluations for each point in the input adaptation data set in order to generate the prediction data set.
14. The color processing system of claim 12 , wherein the characterization system is operative for each point in the input adaptation data set to subtract the values of the prediction data set from the values of the measured adaptation data set in order to generate the prediction error data set.
15. The color processing system of claim 12 , wherein the characterization system is operative to fit a smooth membrane surface to the prediction error data set in order to generate the membrane forward color transform.
16. The color processing device of claim 12 , wherein the rendering system comprises a plurality of marking devices operative according to the device dependent color data to transfer marking material onto a corresponding medium to create visible test images on the medium.