Image processing device, image processing method and image processing program storage medium

Abstract

An image processing device includes a conversion section that converts an input image signal to an out put image signal within a color gamut of an output device by a predetermined conversion function, a storage section that stores a target value for a predetermined color and a predetermined standard gradation characteristic, and a determination section that determines the conversion function such that a gradation characteristic of the output image signal accords with at least a portion of the standard gradation characteristic. The conversion function is determined on the basis of the input signal, the target value for the predetermined color and the predetermined standard gradation characteristic.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a block diagram showing an example of schematic structure of an image processing device relating to an exemplary embodiment of the present invention.

FIG. 2 is a block diagram showing an example of schematic structure of a color space signal conversion section of the image processing device.

FIG. 3 is a diagram for describing a gradation characteristic.

FIG. 4 is a diagram for describing the gradation characteristic.

FIG. 5 is a flowchart showing an example of a processing sequence of an image processing method relating to the exemplary embodiment of the present invention.

FIG. 6 is the flowchart showing the example of the processing sequence of the image processing method relating to the exemplary embodiment of the present invention.

FIG. 7 is a conceptual diagram showing an example of a color gamut.

FIG. 8 is a conceptual diagram of processing for conversion of a hue at a hue conversion section.

FIG. 9 is a diagram for describing a case in which a target point is outside a color gamut.

FIG. 10 is an explanatory diagram showing a specific example of color conversion processing for a case in which a brightness indicated by an intermediate image signal is higher than a cusp point brightness.

FIG. 11 is an explanatory diagram showing a specific example of color conversion processing for a case in which a brightness indicated by an intermediate image signal is lower than a cusp point brightness.

FIG. 12 is an explanatory diagram showing an example of non-linear compression mapping processing.

FIG. 13 is an explanatory diagram showing an example of color conversion processing for a case in which a point representing an intermediate image signal is located outside an intermediate color gamut.

Claims

1. An image processing device comprising: a conversion section that converts an input image signal to an output image signal within a color gamut of an output device by a predetermined conversion function;a storage section that stores a target value for a predetermined color and a predetermined standard gradation characteristic; anda determination section that, on the basis of the input image signal, the target value for the predetermined color and the predetermined standard gradation characteristic, determines the conversion function such that a gradation characteristic of the output image signal accords with at least a portion of the standard gradation characteristic.

2. The image processing device of claim 1, wherein the determination section determines the conversion function such that the gradation characteristic for at least one of low saturation or high brightness accords with the standard gradation characteristic.

3. The image processing device of claim 1, wherein the gradation characteristic is represented by at least one of a color difference or a distance on a locus from a first predetermined position with low saturation to a second predetermined position within a predetermined color gamut.

4. The image processing device of claim 1, wherein the gradation characteristic is represented by at least one of a color difference or a distance on a locus in a hue direction from a first predetermined position to a second predetermined position within a predetermined color gamut.

5. The image processing device of claim 1, wherein the gradation characteristic comprises a gradation characteristic of a region with a brightness smaller than a brightness at a maximum saturation point in a predetermined color gamut, and is represented in a transformation direction of a mixing characteristic of a colorant.

6. The image processing device of claim 1, wherein the storage section stores, for each of color reproduction objectives, at least one of the target value for the predetermined color or standard gradation characteristic data relating to the predetermined standard gradation characteristic.

7. The image processing device of claim 1, wherein the predetermined color includes at least one of a saturated color of a prime color, an intermediate color, a color that is to be similarly reproduced at a plurality of output devices, or a color specified by a user.

8. The image processing device of claim 7, wherein the color that is to be similarly reproduced is set in a vicinity of a prime color in the color gamut of the output device.

9. The image processing device of claim 7, wherein, if there is another target value for a color in a vicinity of the target value for the color specified by a user, the color specified by a user is given priority.

10. The image processing device of claim 1, wherein the target value for the predetermined color is determined in accordance with an area ratio in the color space of the output device and is represented by a level of color purity, and the predetermined color is in a vicinity of a prime color.

11. The image processing device of claim 1, wherein, if the target value is outside the color gamut of the output device, a point on an outer border of the color gamut that is a point at which a color difference from the target value is minimal is set as the target value.

12. The image processing device of claim 1, further comprising an edge correction section that, if an edge line linking points of maximum saturation of a predetermined color gamut includes a portion that varies locally, performs correction so as to smoothen this portion.

13. The image processing device of claim 1, wherein the storage section stores the conversion function determined by the determination section, and the image processing device further comprises a function correction section that corrects the conversion function on the basis of information of alteration, if a characteristic of the predetermined color or the gradation characteristic is to be altered according to an outputted color.

14. The image processing device of claim 1, wherein the gradation characteristic is set on the basis of outer border information that represents an outer border of at least one of color gamuts of an input device and the output device.

15. An image processing method comprising: converting an input image signal to an output image signal within a color gamut of an output device by a predetermined conversion function;determining the conversion function such that a gradation characteristic of the output image signal accords with at least a portion of a standard gradation characteristic on the basis of the input image signal, a target value of a predetermined color and the predetermined standard gradation characteristic.

16. The image processing method of claim 15, wherein the conversion function is determined such that the gradation characteristic for at least one of low saturation or high brightness accords with the standard gradation characteristic.

17. The image processing method of claim 15, wherein the gradation characteristic is represented by at least one of a color difference or a distance on a locus from a first predetermined position with low saturation to a second predetermined position within a predetermined color gamut.

18. The image processing method of claim 15, wherein the gradation characteristic is represented by at least one of a color difference or a distance on a locus in a hue direction from a first predetermined position to a second predetermined position within a predetermined color gamut.

19. The image processing method of claim 15, wherein the gradation characteristic comprises a gradation characteristic of a region with a brightness smaller than a brightness at a maximum saturation point in a predetermined color gamut, and is represented in a transformation direction of a mixing characteristic of a colorant.

20. A storage medium storing an image processing program for execution by a computer of image processing, the image processing comprising: converting an input image signal to an output image signal within a color gamut of an output device by a predetermined conversion function;determining the conversion function such that a gradation characteristic of the output image signal accords with at least a portion of a standard gradation characteristic on the basis of the input image signal, a target value of a predetermined color stored in the storage section and the predetermined standard gradation characteristic stored in a storage section.