Color gamut mapping using a cost function
A method of generating a reduced color gamut boundary for a color output device using three or more colorants, wherein the amount of each colorant is controlled by a colorant control signal vector, including determining a forward device model for the color output device relating the colorant control signal vector to the corresponding output color; determining a complete color gamut boundary for the color output device, comprising a set of color gamut boundary points; and determining a set of candidate colorant control signal vectors for each point in the complete color gamut boundary. The method also includes selecting a preferred colorant control signal vector.
1. A method of generating a reduced color gamut boundary for a color output device, the color output device producing output colors using three or more colorants, wherein the amount of each colorant is controlled by a colorant control signal vector, comprising the steps of:
a) determining a forward device model for the color output device relating the colorant control signal vector to the corresponding output color;
b) determining a complete color gamut boundary for the color output device, comprising a set of color gamut boundary points;
c) determining a set of candidate colorant control signal vectors for each point in the complete color gamut boundary;
d) selecting a preferred colorant control signal vector from the set of candidate colorant control signal vectors for each point in the complete color gamut boundary using a cost function responsive to one or more cost attribute(s) that vary as a function of the colorant control signal vector; and
e) defining a reduced color gamut boundary comprising a set of output colors by using the forward device model to determine the output colors for each of the preferred colorant control signal vectors.
2. The method of claim 1 wherein step a) includes producing a set of color patches corresponding to a set of colorant control signal vectors and measuring the output color of each color patch.
3. The method of claim 1 wherein the color output device uses at least cyan, magenta, yellow, and black colorants.
4. The method of claim 1 wherein one of the cost attributes is a total colorant amount.
5. The method of claim 1 wherein one of the cost attributes is a colorimetric cost term.
6. The method of claim 1 wherein one of the cost attributes is an image noise metric.
7. The method of claim 6 wherein the image noise metric is determined from an image noise model that relates the colorant control signal vector to the corresponding image noise metric.
8. The method of claim 7 wherein the image noise model is formed by producing a set of color patches corresponding to a set of colorant control signal vectors and measuring the image noise metric of each color patch.
9. The method of claim 1 wherein one of the cost attributes is a function of the amount of an individual colorant.
10. The method of claim 9 wherein the cost attribute increases with the amount of a black colorant.
11. The method of claim 1 wherein one of the cost attributes is a metameric index.
12. The method of claim 1 wherein one of the cost attributes is a surface gloss value.
13. The method of claim 1 wherein one of the cost attributes is a waterfastness value.
14. The method of claim 1 wherein one of the cost attributes is a lightfastness value.
15. The method of claim 1 further including the step of using the reduced color gamut boundary, together with a gamut-mapping algorithm, to process colors outside of the reduced color gamut boundary to determine corresponding gamut-mapped colors that lie on or inside the reduced color gamut boundary.
16. A computer storage product having at least one computer storage medium having instructions stored therein causing one or more computers to perform the method of claim 1 .