Color adjustment method, color adjustment apparatus, color conversion definition editing apparatus, image processing apparatus, program, and storage medium

• US 20040057614A1
• Filed: 03/12/2003
• Published: 03/25/2004
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Original Assignee: Fuji Xerox Company Limited (Xerox Holdings Corp.)
• Inventors: Ikegami, Hiroaki, Ogatsu, Hitoshi
• Granted Patent: US 7,333,237 B2
• Time in Patent Office: Days
• US Class Current: 382/162
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

Adjustment object color space containing movement source partial color space including a color of an object of conversion processing and movement destination partial color space including a color in which the conversion processing is performed so as to inscribe the spaces is handled as a conversion object region. The inside of the conversion object region is moved toward a target color so that coordinates of an adjustment object overlaps with coordinates of a point after movement and the boundary of a movement region moves little or does not move at all. As a result of this, a phenomenon such as a color jump or gradation inversion occurs little in the boundary portion to the outside of an adjustment object region. Therefore, maintenance of gradation continuity of an image of a color adjustment object and prevention of color inversion can be combined to make partial color adjustment.

Claims

1. A color adjustment method for obtaining a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the color adjustment method comprising:

obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region,

wherein the adjustment object region includes;

movement source partial color space including a color, which is an object of processing of the color conversion; and

movement destination partial color space including a color corresponding to the obtained coefficient.

3. The color adjustment method according to claim 1, further comprising:

determining a representative color, which represents colors in the movement source partial color space;

determining a target color, which represents colors in the movement destination partial color space and a target of the color processed by the color conversion;

obtaining a fundamental vector indicating movement in the color space from the representative color to the target color;

moving image data included in the adjustment object region in the color space in accordance with a direction and a distance, which the fundamental vector indicates; and

making an amount of the movement at boundary of the adjustment object region be substantially zero.

4. The color adjustment method according to claim 3, further comprising:

performing coordinate conversion by revolution displacement so that a straight line connecting the representative color and the target color is parallel to one of color space coordinate axes indicating the adjustment object region;

performing the color conversion processing with respect to inside of the adjustment object region; and

performing inverse transformation of the coordinate conversion by the revolution displacement.

5. The color adjustment method according to claim 3, further comprising:

setting a primary region fully containing the adjustment object region on the input color space;

determining as to whether pixel data, which an input color signal indicates, is located inside or outside the primary region;

performing coordinate conversion by revolution displacement with respect to the pixel data, which is determined to be located inside the primary region, so that a straight line connecting the representative color and the target color is parallel to one of color space coordinate axes indicating the adjustment object region;

determining, with respect to the color signal on which the revolution displacement is performed and the color signal on which the revolution displacement is not performed, as to whether or not the pixel data, which each of color signals indicates, is located inside or outside the adjustment object region;

performing the color conversion processing with respect to the pixel data, which is determined to be located inside the adjustment object region; and

performing inverse transformation of the coordinate conversion by the revolution displacement with respect to the pixel data, which is performed the color conversion processing.

6. The color adjustment method according to claim 3, further comprising:

performing coordinate conversion by parallel displacement so that one of the representative color and the target color is moved to the origin of color space coordinate axis indicating the adjustment object region;

performing the color conversion processing with respect to inside of the adjustment object region; and

performing inverse transformation of the coordinate conversion by the parallel displacement.

7. The color adjustment method according to claim 3, further comprising:

setting a primary region substantially fully containing the adjustment object region on the input color space;

determining as to whether pixel data, which an input color signal indicates, is located inside or outside the primary region;

performing coordinate conversion by parallel displacement with respect to the pixel data, which is determined to be located inside the primary region, so that one of the representative color and the target color is moved to the origin of color space coordinate axes indicating the adjustment object region;

determining, with respect to the color signal on which the parallel displacement is performed and the color signal on which the parallel displacement is not performed, as to whether or not the pixel data, which each of color signals indicates, is located inside or outside the adjustment object region;

performing the color conversion processing with respect to the pixel data, which is determined to be located inside the adjustment object region; and

performing inverse transformation of the coordinate conversion by the parallel displacement with respect to the pixel data, which is performed the color conversion processing.

8. The color adjustment method according to claim 1, further comprising:

setting a convergence region in a part of the adjustment object region; and

obtaining, with respect to a process objection portion, which is in the adjustment object region and other than the convergence region, a coefficient for converting the color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of the gradations and not causing the color inversion within the adjustment object region.

2. A color adjustment method for obtaining a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the color adjustment method comprising:

obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region,

wherein movement source partial color space includes a color, which is an object of processing of the color conversion;

wherein movement destination partial color space includes a color corresponding to the obtained coefficient; and

wherein the movement source partial color space and the movement destination partial color space inscribe the adjustment object region.

9. A color adjustment apparatus for obtaining a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the color adjustment apparatus comprising:

a coefficient acquisition section for obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region.

10. The color adjustment apparatus according to claim 9, wherein:

the coefficient acquisition section determines a representative color, which represents colors in movement source partial color space;

the coefficient acquisition section determines a target color, which represents colors in movement destination partial color space and a target of the color processed by the color conversion;

the coefficient acquisition section obtains a fundamental vector indicating movement in the color space from the representative color to the target color;

the coefficient acquisition section moves image data included in the adjustment object region in the color space in accordance with a direction and a distance, which the fundamental vector indicates;

the coefficient acquisition section makes an amount of the movement at boundary of the adjustment object region be substantially zero;

the movement source partial color space includes a color, which is an object of processing of the color conversion; and

the movement destination partial color space includes a color corresponding to the obtained coefficient.

11. The color adjustment apparatus according to claim 10, further comprising:

a movement process section for performing coordinate conversion by revolution displacement so that a straight line connecting the representative color and the target color is parallel to one of color space coordinate axes indicating the adjustment object region;

a color adjustment conversion section for performing the color conversion processing with respect to inside of the adjustment object region; and

an inverse transformation process section for performing inverse transformation of the coordinate conversion by the revolution displacement.

12. The color adjustment apparatus according to claim 10, further comprising:

a primary-region inside/outside determination section for setting a primary region substantially fully containing the adjustment object region on the input color space, and determining as to whether pixel data, which an input color signal indicates, is located inside or outside the primary region;

a movement process section for performing coordinate conversion by revolution displacement with respect to the pixel data, which is determined to be located inside the primary region by the primary-region inside/outside determination section, so that a straight line connecting the representative color and the target color is parallel to one of color space coordinate axes indicating the adjustment object region;

a secondary-region inside/outside determination section for determining, with respect to the color signal on which the revolution displacement is performed by the movement process section and the color signal on which the revolution displacement is not performed, as to whether or not the pixel data, which each of color signals indicates, is located inside or outside the adjustment object region;

a color adjustment conversion section for performing the color conversion processing with respect to the pixel data, which is determined to be located inside the adjustment object region by the secondary-region inside/outside determination section; and

an inverse transformation process section for performing inverse transformation of the coordinate conversion by the revolution displacement with respect to the pixel data, which is performed the color conversion processing by the color adjustment conversion section.

13. The color adjustment apparatus according to claim 10, further comprising:

a movement process section for performing coordinate conversion by parallel displacement so that one of the representative color and the target color is moved to the origin of color space coordinate axis indicating the adjustment object region;

a color adjustment conversion section for performing the color conversion processing with respect to inside of the adjustment object region; and

an inverse transformation process section for performing inverse transformation of the coordinate conversion by the parallel displacement.

14. The color adjustment apparatus according to claim 10, further comprising:

a primary-region inside/outside determination section for setting a primary region substantially fully containing the adjustment object region on the input color space, and determining as to whether pixel data, which an input color signal indicates, is located inside or outside the primary region;

a movement process section for performing coordinate conversion by parallel displacement with respect to the pixel data, which is determined to be located inside the primary region by the primary-region inside/outside determination section, so that one of the representative color and the target color is moved to the origin of color space coordinate axes indicating the adjustment object region;

a secondary-region inside/outside determination section for determining, with respect to the color signal on which the parallel displacement is performed by the movement process section and the color signal on which the parallel displacement is not performed, as to whether or not the pixel data, which each of color signals indicates, is located inside or outside the adjustment object region;

a color adjustment conversion section for performing the color conversion processing with respect to the pixel data, which is determined to be located inside the adjustment object region by the secondary-region inside/outside determination section; and

an inverse transformation process section for performing inverse transformation of the coordinate conversion by the parallel displacement with respect to the pixel data, which is performed the color conversion processing by the color adjustment conversion section.

15. The color adjustment apparatus according to claim 10, wherein at least one of the movement source partial color space and the movement destination partial color space is defined based on a shape thereof and a center coordinate responding to the shape thereof.

16. The color adjustment apparatus according to claim 10, wherein at least one of the movement source partial color space and the movement destination partial color space has a shape, which is one of a sphere shape, a ellipsoidal shape, a cylindrical shape, a elliptic cylinder shape, a rectangular parallelepiped shape, and a closed solid shape at least other than a torus shape.

17. The color adjustment apparatus according to claim 9, wherein the color space of a color signal, which is processed by the coefficient acquisition section when the coefficient is obtained, is device-independent color space.

18. The color adjustment apparatus according to claim 9, wherein the color space of a color signal, which is processed by the coefficient acquisition section when the coefficient is obtained, be device-dependent color space.

19. The color adjustment apparatus according to claim 9, wherein:

the coefficient acquisition section sets a convergence region in a part of the adjustment object region; and

the coefficient acquisition section obtains, with respect to a process objection portion, which is in the adjustment object region and other than the convergence region, the coefficient for converting the color within the adjustment object region into the another color on the output color space, which is the same color space as the input color space, with maintaining continuity of the gradations and not causing the color inversion within the adjustment object region.

20. The color adjustment apparatus according to claim 10, further comprising:

a movement parameter setting section for selecting a specified color chart from a plurality of color charts displayed on a predetermined display medium to specify at least one of color coordinates of the representative color and color coordinates of the target color,

wherein the coefficient acquisition section executes the process for obtaining the coefficient based on the color coordinates specified by the movement parameter setting section.

21. The color adjustment apparatus according to claim 10, further comprising:

a movement parameter setting section for selecting a receiving specification of pixel point in the color image displayed on a predetermined display medium to specify at least one of color coordinates of the representative color and color coordinates of the target color,

wherein the coefficient acquisition section executes the process for obtaining the coefficient based on the color coordinates specified by the movement parameter setting section.

22. The color adjustment apparatus according to claim 10, further comprising:

a movement parameter setting section for specifying at least one of a shape of the movement source partial color space and a shape of the movement destination partial color space,

wherein the coefficient acquisition section executes the process for obtaining the coefficient based on the shape specified by the movement parameter setting section.

23. The color adjustment apparatus according to claim 10, further comprising:

a movement parameter setting section for specifying, in response to at least one of a shape of the movement source partial color space and a shape of the movement destination partial color space, a size of the shape corresponding to specification of radius with respect to a sphere shape,

wherein the coefficient acquisition section executes the process for obtaining the coefficient based on the size of the shape specified by the movement parameter setting section.

24. A color conversion definition editing apparatus for editing a color conversion definition including a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the color conversion definition editing apparatus comprising:

a color adjustment apparatus including a coefficient acquisition section for obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region; and

a coefficient editing section for replacing the coefficient obtained by the coefficient acquisition section with a coefficient of the color conversion definition, which is prepared in advance, to edit the color conversion definition, wherein;

the coefficient acquisition section determines a representative color, which represents colors in movement source partial color space;

the coefficient acquisition section determines a target color, which represents colors in movement destination partial color space and a target of the color processed by the color conversion;

the coefficient acquisition section obtains a fundamental vector indicating movement in the color space from the representative color to the target color;

the coefficient acquisition section moves image data included in the adjustment object region in the color space in accordance with a direction and a distance, which the fundamental vector indicates; and

the coefficient acquisition section makes an amount of the movement at boundary of the adjustment object region be substantially zero.

25. The color conversion definition editing apparatus according to claim 24, wherein:

movement source partial color space includes a color, which is an object of processing of the color conversion;

movement destination partial color space includes a color corresponding to the obtained coefficient;

the coefficient included in the color conversion definition is data of a lattice point of at least one dimension look-up table; and

the coefficient editing section makes at least one of the lattice point of the look-up table be color coordinates of representative color of the movement source partial color space.

26. The color conversion definition editing apparatus according to claim 25, wherein:

the coefficient acquisition section sets a convergence region in a part of the adjustment object region;

the coefficient acquisition section obtains, with respect to a process objection portion, which is in the adjustment object region and other than the convergence region, the coefficient for converting the color within the adjustment object region into the another color on the output color space, which is the same color space as the input color space, with maintaining continuity of the gradations and not causing the color inversion within the adjustment object region;

the coefficient included in the color conversion definition is data of a lattice point of at least one dimension look-up table; and

the coefficient editing section sets the convergence region so as to include at least two lattice points of the look-up table.

27. An image processing apparatus for converting, with respect to a predetermined adjustment object region within color space to which a color image belongs, a color into another color on the same color space to convert a specific color included an input color image into the another color, the image processing apparatus comprising:

a color adjustment apparatus including a coefficient acquisition section for obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region; and

a partial color adjustment section for moving pixel data indicating color of each pixel included in the adjustment object region extracted from the input color image in the color space based on the coefficient obtained by the coefficient acquisition section to perform color conversion.

28. An image processing apparatus for converting, with respect to a predetermined adjustment object region within color space to which a color image belongs, a color into another color on the same color space to convert a specific color included an input color image into the another color, the image processing apparatus comprising:

a storage section for storing a color conversion definition; and

a partial color adjustment section for converting pixel data indicating color of each pixel included in the adjustment object region extracted from the input color image in the color space based on the color conversion definition stored by the storage section, wherein

the color conversion definition is edited by a color conversion definition editing apparatus for editing the color conversion definition including a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the color conversion definition editing apparatus including;

a color adjustment apparatus including a coefficient acquisition section for obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region; and

a coefficient editing section for replacing the coefficient obtained by the coefficient acquisition section with a coefficient of the color conversion definition, which is prepared in advance, to edit the color conversion definition;

the coefficient acquisition section determines a representative color, which represents colors in movement source partial color space;

the coefficient acquisition section determines a target color, which represents colors in movement destination partial color space and a target of the color processed by the color conversion;

the coefficient acquisition section obtains a fundamental vector indicating movement in the color space from the representative color to the target color;

the coefficient acquisition section moves image data included in the adjustment object region in the color space in accordance with a direction and a distance, which the fundamental vector indicates; and

the coefficient acquisition section makes an amount of the movement at boundary of the adjustment object region be substantially zero.

29. A program for obtaining a coefficient for performing a process for obtaining a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the program comprising:

making a computer serve as a coefficient acquisition section, wherein;

the coefficient acquisition section obtains a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region.

30. A computer readable storage medium storing a program for obtaining a coefficient for performing color conversion of input color space into output color space with respect to a predetermined adjustment object region within color space to which a color image belongs, the program causing a computer to conduct a procedure comprising:

obtaining a coefficient for converting a color within the adjustment object region into another color on the output color space, which is the same color space as the input color space, with maintaining continuity of gradations and not causing color inversion within the adjustment object region.