Color processing device, color processing method, and computer readable medium storing program

1. A color processing device comprising:

a calculating unit that:

calculates hues in a device-dependent color space of an input side device; and

calculates hues in a device-independent color space of an output side device of a plurality of reproduction colors that are positioned on an input color gamut boundary and that have different hues;

a deriving unit that is configured to derive a correspondence between the hues in the device-dependent color space and the hues of the corresponding colors in the device-independent color space on the basis of the hues in the device-independent color space calculated by the calculating unit, by calculating, on the plurality of reproduction colors, individual hues of corresponding colors in which a determined difference in at least one of lightness and chroma caused by color gamut mapping performed in the device-independent color space is smaller than a determined difference caused by the color gamut mapping performed on the plurality of the reproduction colors;

a hue correcting unit that is configured to correct input colors so that hues in the device-independent color space of the input colors become similar to the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space of the input colors obtained by calculating, using the correspondence derived by the deriving unit, hues in the device-dependent color space from the input colors; and

a color gamut mapping unit that performs the color gamut mapping in which the input colors corrected by the hue correcting unit are mapped into an output color gamut in the device-independent color space.

2. The color processing device according to claim 1 , wherein the deriving unit calculates, as the hues of the corresponding colors, hues of colors that are positioned on a boundary of the output color gamut in the device-independent color space and that have a smallest color difference in the device-independent color space with respect to the reproduction colors or a smallest value of an evaluation function correlated with the color difference.

3. The color processing device according to claim 1 , wherein the deriving unit calculates, as the hues of the corresponding colors, hues of colors in which a hue difference from the hues in the device-independent color space of the reproduction colors is equal to or smaller than a predetermined threshold.

4. The color processing device according to claim 1 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, then determines the amount of change from the hues in the device-independent color space of the input colors to the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space of the input colors in accordance with a ratio of chroma in the device-independent color space of the reproduction colors and chroma in the device-independent color space of the input colors, and determines the hues of the corresponding colors on the basis of the determined amount of change.

5. The color processing device according to claim 2 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, then determines the amount of change from the hues in the device-independent color space of the input colors to the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space of the input colors in accordance with a ratio of chroma in the device-independent color space of the reproduction colors and chroma in the device-independent color space of the input colors, and determines the hues of the corresponding colors on the basis of the determined amount of change.

6. The color processing device according to claim 3 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, then determines the amount of change from the hues in the device-independent color space of the input colors to the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space of the input colors in accordance with a ratio of chroma in the device-independent color space of the reproduction colors and chroma in the device-independent color space of the input colors, and determines the hues of the corresponding colors on the basis of the determined amount of change.

7. The color processing device according to claim 1 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, calculates the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space on the basis of the correspondence, and corrects input colors in which a difference between the hue in the device-independent color space and the hue of the corresponding color in the device-independent color space is larger than a predetermined threshold among the input colors so that the difference becomes equal to or smaller than the threshold.

8. The color processing device according to claim 2 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, calculates the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space on the basis of the correspondence, and corrects input colors in which a difference between the hue in the device-independent color space and the hue of the corresponding color in the device-independent color space is larger than a predetermined threshold among the input colors so that the difference becomes equal to or smaller than the threshold.

9. The color processing device according to claim 3 , wherein the hue correcting unit calculates the hues in the device-dependent color space and the hues in the device-independent color space from the input colors, calculates the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space on the basis of the correspondence, and corrects input colors in which a difference between the hue in the device-independent color space and the hue of the corresponding color in the device-independent color space is larger than a predetermined threshold among the input colors so that the difference becomes equal to or smaller than the threshold.

10. A color processing method comprising:

calculating hues in a device-dependent color space of an input side device;

calculating hues in a device-independent color space of an output side device of a plurality of reproduction colors that are positioned on an input color gamut boundary and that have different hues;

deriving a correspondence between the hues in the device-dependent color space and the hues of the corresponding colors in the device-independent color space, on the basis of the calculated hues in the device-independent color space, by calculating, on the plurality of reproduction colors, individual hues of corresponding colors in which a determined difference in at least one of lightness and chroma caused by color gamut mapping performed in the device-independent color space is smaller than a determined difference caused by the color gamut mapping performed on the reproduction colors;

correcting the input colors so that hues in the device-independent color space of the input colors become similar to the hues of the corresponding colors in the device-independent color space corresponding to the hues in the device-dependent color space of the input colors obtained by calculating, using the correspondence derived by the deriving unit, hues in the device-dependent color space from input colors; and

performing the color gamut mapping in which the corrected input colors are mapped into an output color gamut in the device-independent color space.

11. A non-transitory computer readable medium storing a program causing a computer to execute a process for processing colors, the process comprising:

calculating hues in a device-dependent color space of an input side device;

calculating hues in a device-independent color space of an output side device of a plurality of reproduction colors that are positioned on an input color gamut boundary and that have different hues;

deriving a correspondence between the hues in the device-dependent color space and the hues of the corresponding colors in the device-independent color space, on the basis of the calculated hues in the device-independent color space, by calculating, on the plurality of reproduction colors, individual hues of corresponding colors in which a determined difference in at least one of lightness and chroma caused by color gamut mapping performed in the device-independent color space is smaller than a determined difference caused by the color gamut mapping performed on the reproduction colors;

correcting the input colors so that hues in the device-independent color s ace of the input colors become similar to the hues of the corresponding colors in the device-independent colors space corresponding to the hues in the device-dependent color space of the input colors obtained by calculating, using the correspondence derived by the deriving unit, hues in the device-dependent color space from input colors; and

performing the color gamut mapping in which the corrected input colors are mapped into an output color gamut in the device-independent color space.