System and method for color space conversion

• US 5,946,113 A
• Filed: 03/29/1996
• Issued: 08/31/1999
• Est. Priority Date: 03/29/1996
• Status: Expired due to Term

• Current Assignee: Open Invention Network LLC
• Original Assignee: Silicon Graphics Incorporated (Graphics Properties Holdings, Inc.)
• Inventors: Pritchett, Scott K.
• Primary Examiner(s): Lee, Thomas D.
• Assistant Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US08/623,703
• Time in Patent Office: 1,250 Days
• Field of Search: 358/504, 358/515-523, 358/539, 348/223, 348/557, 348/577, 348/603
• US Class Current: 358/520
• CPC Class Codes: H04N 1/6058 Reduction of colour to a range of reproducible colours, e.g. to ink- reproducible colour gamut
• CPC Class Codes: H04N 9/67 for matrixing camera processing pipelines for matrixing of colour signals H04N23/85
• CPC Class Codes: H04N 9/68 for controlling the amplitude of colour signals, e.g. automatic chroma control circuits H04N9/71, H04N9/73 take precedence; camera processing pipelines for controlling the colour saturation of colour signals H04N23/86

Abstract

A system and method for converting a color uses an extended color space to convert a color from a first color space to a second color space. The extended color space is extended from the second color space. In other words, the extended color space has increased valid component ranges compared with the second color space to accommodate the conversion of any valid colors from the first color space. Subsequent operations on the converted color in the extended color space occur without the presence of conversion artifacts found in many conventional color space converters.

Claims

1. A method for converting a representation of a color in a first color space to a corresponding representation of the color in a second color space using an extended color space to accommodate invalid colors in the second color space, the method comprising the steps of:

adjusting the representation of the color by an input offset value to obtain an adjusted representation of the color, said input offset value compensating for any bias present in the first color space;

applying a conversion matrix to said adjusted representation of the color to obtain a converted representation of the color, said conversion matrix defining a relationship between said first color space and said second color space;

adjusting said converted representation of the color by an output offset value to obtain a corresponding representation of the color in the extended color space, said output offset value compensating for any desired bias in the second color space, wherein the representation of the color is a valid color in the first color space and wherein the corresponding representation of the color is an invalid color in the second color space, the extended color space being an extended version of the second color space to accommodate said invalid color in the second color space; and

operating on said corresponding representation of the color in the extended color space to produce a modified color representation in the extended color space having no conversion artifacts.

2. The method of claim 1, further comprising, after the step of operating, the step of adjusting said modified representation of the color in the extended color space so that said modified representation of the color is a valid color with respect to the second color space.

3. The method of claim 1, further comprising, after the step of operating, the step of converting said modified representation of the color in the extended color space back to a representation of the modified color in the first color space.

4. The method of claim 1, further comprising, after the step of operating, the step of converting said modified representation of the color in the extended color space to a representation of the modified color in a third color space.

5. A method for operating in a second color space on a color represented in a first color space, the method comprising the steps of:

converting the color from a representation in the first color space to a representation in an extended color space, wherein the color is a valid color in the first color space and an invalid color in the second color space, wherein said extended color space is an extended version of the second color space to accommodate said invalid color in the second color space; and

operating on said representation of the color in said extended color space to obtain a modified representation of the color in the extended color space so that conversion artifacts are not introduced into the color.

6. The method of claim 5, further comprising the step of:

converting said modified representation of the color in said extended color space to a corresponding modified representation of the color in the first color space.

7. The method of claim 5, wherein said step of converting further comprises the step of:

adjusting said representation of the color in the first color space by an input offset value to remove any bias present therein.

8. The method of claim 5, wherein said step of converting further comprises the step of:

adjusting said representation of the color in the extended color space by an output offset value to introduce any bias desired therein.

9. The method of claim 5, wherein said step of converting further comprises the step of:

adjusting said representation of the color in the first color space to remove any bias present in the first color space and to introduce any bias desired in the extended color space.

10. An imaging system comprising:

a video source for supplying a video image;

a computer for displaying a computer graphic image;

a converter, coupled to said video source and said computer, for converting said video image into said computer graphic image corresponding to said video image, said converter further comprising;

a color space converter for converting a representation of a color in a color space of said video image to a representation of said color in an extended color space, said color being a valid color in said color space of said video image and an invalid color in a color space of said computer graphic image, said extended computer color space being an extended version of said color space of said computer graphic image; and

an imaging operator for performing operations on said computer graphic image to obtain a modified image in said extended color space, said imaging operator performing said operations on said representation of said color in said extended color space so that conversion artifacts are not introduced into said modified image.

11. The system of claim 10, wherein said color space converter further comprises:

offset adjust means for adjusting for any biases that exist in said color space of said video image and said color space of said computer graphic image.

12. The system of claim 11, wherein said offset adjust means comprises:

input offset adjust means for removing any bias present in said color space of said video image.

13. The system of claim 11, wherein said offset adjust means comprises:

output offset adjust means for introducing any desired bias in said color space of said computer graphic image.

14. The system of claim 11, wherein said offset adjust means comprises:

input offset adjust means for removing any bias present in said color space of said video image; and

output offset adjust means for introducing any desired bias in said color space of said computer graphic image.

15. The system of claim 11, further comprising:

a second converter, coupled to said computer and a video destination, for converting said modified image into a modified video image corresponding to said modified image, said second converter further comprising;

a second color space converter for converting said representation of said color in said extended color space to a corresponding representation of said color in a color space of said modified video image.

16. The system of claim 15, wherein said color space of said modified video image and said color space of said video image are identical.

17. The system of claim 10, further comprising:

a post processor, coupled to said imaging operator, having means for adjusting said representation of said color in said extended color space to a corresponding representation of said color in said color space of said computer graphics image.

18. The system of claim 17, wherein said means for adjusting comprises clamping said representation of said color in said extended color space to a valid range of said color space of said computer graphics image.