Methods and systems for color gamut adjustment

• US 20060176528A1
• Filed: 02/08/2005
• Published: 08/10/2006
• Est. Priority Date: 02/08/2005
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Dalrymple, John C., Chang, James Z.
• Granted Patent: US 7,742,206 B2
• Time in Patent Office: Days
• US Class Current: 358/518
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut

Abstract

Embodiments of the present invention comprise methods and systems for color gamut mapping.

Claims

1. A method for color gamut adjustment, said method comprising:

a) determining a plurality of gamut points in a color space, wherein said gamut points represent the limits of a color-rendering capability of an output device;

b) modeling at least a portion of said gamut points with a curvilinear construct;

c) mapping a designated color that falls outside said color-rendering capability limits to a color that is within said limits by a method comprising;

i) projecting a color point representing said designated color onto said curvilinear construct, and

ii) projecting from said curvilinear construct onto a mapped color point within said limits; and

d) using the color corresponding to said mapped color point to represent said designated color.

2. A method as described in claim 1 wherein said projecting a color point comprises projecting said color point in a direction perpendicular to said curvilinear construct.

3. A method as described in claim 1 wherein said projecting a color point comprises projecting said color point in a direction of constant lightness.

4. A method as described in claim 1 wherein said projecting a color point comprises projecting said color point to a nearest point on said curvilinear construct.

5. A method as described in claim 1 wherein said projecting from said curvilinear construct comprises projecting in a direction perpendicular to a shape connecting said gamut points.

6. A method as described in claim 1 wherein said projecting from said curvilinear construct comprises projecting in a direction of constant lightness.

7. A method as described in claim 1 wherein said projecting from said curvilinear construct comprises projecting to the nearest point of said gamut points.

8. A method for color gamut adjustment, said method comprising:

a) determining a plurality of gamut points in a color space, wherein said gamut points represent the limits of a color-rendering capability of an output device;

b) modeling at least a portion of said gamut points with a curvilinear construct;

c) mapping a designated color that falls outside said color-rendering capability limits to a color that is within said limits by a method comprising;

i) projecting a color point representing said designated color onto said curvilinear construct thereby defining an initial projection point, and

ii) projecting said initial projection point onto a mapped color point within said gamut points; and

d) using the color corresponding to said mapped color point to represent said designated color.

9. A method as described in claim 8 wherein said projecting a color point comprises projecting said color point in a direction perpendicular to said curvilinear construct.

10. A method as described in claim 8 wherein said projecting a color point comprises projecting said color point in a direction of constant lightness.

11. A method as described in claim 8 wherein said projecting a color point comprises projecting said color point to a nearest point on said curvilinear construct.

12. A method as described in claim 8 wherein said projecting said initial projection point comprises projecting said initial projection point in a direction perpendicular to a shape connecting said gamut points.

13. A method as described in claim 8 wherein said projecting said initial projection point comprises projecting said initial projection point in a direction of constant lightness.

14. A method as described in claim 8 wherein said projecting said initial projection point comprises projecting said initial projection point to the nearest point on a shape connecting said gamut point.

15. A method for color gamut adjustment, said method comprising:

a) determining a plurality of gamut points in a color space, wherein said gamut points represent the limits of a color-rendering capability of an output device;

b) selecting an intermediate point from among said gamut points, wherein said intermediate point divides said gamut points into a first group and a second group;

c) modeling at least one of said groups of gamut points with a curvilinear construct;

d) mapping a designated color that falls outside said gamut points to a color that is within said gamut points by a method comprising;

i) projecting a point representing said designated color onto said curvilinear construct thereby defining an initial projection point, and

ii) projecting said initial projection point onto a mapped color point within said gamut points; and

e) using the color corresponding to said mapped color point to represent said designated color.

16. A method for color gamut adjustment, said method comprising:

a) determining a plurality of gamut points in a color space, wherein said gamut points represent the limits of a color-rendering capability of an output device;

b) selecting a black point that represents black;

c) selecting a white point that represents white;

d) selecting an intermediate point from among said gamut points, wherein said intermediate point divides said gamut points into a first group and a second group;

e) modeling said first group of gamut points with a first curvilinear construct;

f) modeling said second group of gamut points with a second curvilinear construct;

g) establishing a white point regional boundary line commencing at said white point and projecting perpendicularly outwardly relative to said first construct at said white point;

h) establishing a first intermediate point regional boundary line commencing at said intermediate point and projecting perpendicularly outwardly relative to said first construct at said intermediate point;

i) establishing a second intermediate point regional boundary line commencing at said intermediate point and projecting perpendicularly outwardly relative to said second construct at said intermediate point;

j) establishing a black point regional boundary line commencing at said black point and projecting perpendicularly outwardly relative to said second construct at said black point; and

k) mapping colors that fall outside said gamut points to colors within said gamut points by a method comprising;

i) mapping colors in a white region, defined as the area between said white point boundary and a projection of an axis running between said black point and said white point, to the white point;

ii) mapping colors in a black region, defined as the area between said black point boundary and a projection of an axis running between said black point and said white point, to the black point;

iii) mapping colors in a first region, defined as the area lying between said white point regional boundary and said first intermediate point regional boundary, wherein a point representing a color is projected onto said first construct thereby defining an initial projection point, and projecting said initial projection point onto said first group of gamut points;

iv) mapping colors in a second region, defined as the area lying between said first intermediate point regional boundary and said second intermediate point regional boundary, wherein any color in this region is mapped to said intermediate point;

v) mapping colors in a third region, defined as the area lying between said second intermediate point regional boundary and said black point regional boundary, wherein a point representing a color is projected onto said second construct thereby defining an initial projection point, and projecting said initial projection point onto said second group of gamut points.

17. An apparatus for color gamut adjustment, said method comprising:

a) a gamut determiner for determining a plurality of gamut points in a color space, wherein said gamut points represent the limits of a color-rendering capability of an output device;

b) a constructor for modeling at least a portion of said gamut points with a curvilinear construct;

c) a mapper for mapping a designated color that falls outside said color-rendering capability limits to a color that is within said limits, said mapper comprising;

i) a primary projector for projecting a color point representing said designated color onto said curvilinear construct, and

ii) a secondary projector for projecting from said curvilinear construct onto a mapped color point within said limits; and

d) a color assignor for assigning said designated color to the color corresponding to said mapped color point.