Generation of color measured data from transform-based color profiles

• US 20050249403A1
• Filed: 05/05/2004
• Published: 11/10/2005
• Est. Priority Date: 05/05/2004
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Haikin, John S.
• Granted Patent: US 7,483,170 B2
• Time in Patent Office: Days
• US Class Current: 382/162
• CPC Class Codes: G06T 7/90 Determination of colour characteristics
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence

Abstract

Color measurements are generated from transform-based device profiles for use in a measurement-based color management system. The color measurements is generated by providing device-dependent color samples to a transform-based color management module and converting them to the profile connection space with the device'"'"'s transform-based profile. Color measurements are then generated from the transform-based color management module by applying an identity profile in place of a destination device profile. In addition, measurement data can be extracted directly from either the tone reproduction curve/matrix or n-dimensional lookup table transforms contained within a transform-based device profile.

Claims

1. A color management method for generating color measurements for use in a measurement-based color management system, the method comprising the steps of:

accessing a transform-based color profile which contains a color transform for transforming color data from a device-dependent color space to a colorimetric device-independent color space;

generating color measurements using the color transform from the color profile; and

creating a color appearance-based transform using the generated color measurements, wherein the color appearance-based transform is consistent with a color appearance model used by the measurement-based color management system for transforming color image data to an internal color appearance space.

2. The color management method according to claim 1, further comprising the step of:

supplying device-dependent color samples to a transform-based color management module; and

wherein said generating step further includes,

converting the supplied device-dependent color samples to a colorimetric device-independent color space with the color management module by utilizing the color transform contained within the transform-based color profile accessed in said accessing step, and

scaling the converted device-dependent color samples with an identity profile in order to generate the color measurements.

3. The color management method according to claim 2, wherein in the case that the transform-based color profile was not created with measurements taken under a D50 specific illuminant, said generating step further includes,

scaling the generated color measurements with a chromatic adaptation transform contained within the transform-based color profile.

4. The color management method according to claim 3, wherein the transform-based color profile includes a plurality of rendering intents, including an absolute colorimetric rendering intent and a media-relative colorimetric rendering intent.

5. The color management method according to claim 4, wherein the color transform of the transform-based color profile is defined by the absolute colorimetric rendering intent.

6. The color management method according to claim 4, wherein the color transform of the transform-based color profile is defined by the media-relative colorimetric rendering intent.

7. The color management method according to claim 4, wherein the supplied device-dependent color samples are converted into a CIEXYZ color space at a D50 luminance having a power of 500 lux.

8. The color management method according to claim 4, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction of 100.0/65535.0.

9. The color management method according to claim 4, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction 120.0/65535.0.

10. The color management method according to claim 4, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction 150.0/65535.0.

11. The color management method according to claim 4, wherein the color appearance-based transform created in the creating step is in a CIECAM97 format.

12. The color management method according to claim 4, wherein the color appearance-based transform created in the creating step is in a CIECAM02 format.

13. The color management method according to claim 3, wherein the creating step further includes,

unscaling the generated color measurements.

14. The color management method according to claim 1, wherein the color transform is a set of tone reproduction curves and matrix and said generating step further includes,

extracting color measurements from the set of tone reproduction curves and matrix.

15. The color management method according to claim 14, wherein in the case that the transform-based color profile was not created with measurements taken under a D50 specific illuminant, the method further includes the step of:

scaling the extracted color measurements with a chromatic adaptation transform contained within the transform-based color profile.

16. The color management method according to claim 15, wherein the transform-based color profile includes a plurality of rendering intents, including an absolute colorimetric rendering intent and a media-relative colorimetric rendering intent.

17. The color management method according to claim 16, wherein the color transform of the transform-based color profile is defined by the absolute colorimetric rendering intent.

18. The color management method according to claim 16, wherein the color transform of the transform-based color profile is defined by the media-relative colorimetric rendering intent.

19. The color management method according to claim 14, wherein the color appearance-based transform created in the creating step is in a CIECAM97 format.

20. The color management method according to claim 14, wherein the color appearance-based transform created in the creating step is in a CIECAM02 format.

21. The color management method according to claim 1, wherein the color transform is an n-dimensional lookup table and wherein said generating step further includes,

extracting color measurements from the n-dimensional lookup table.

22. The color management method according to claim 21, wherein the n-dimensional lookup table is a three-dimensional lookup table.

23. The color management method according to claim 21, wherein in the case that the transform-based color profile was not created with measurements taken under a D50 specific illuminant, the method further includes the step of:

scaling the extracted color measurements with a chromatic adaptation transform contained within the transform-based color profile.

24. The color management method according to claim 23, wherein the transform-based color profile includes a plurality of rendering intents, including an absolute colorimetric rendering intent and a media-relative colorimetric rendering intent.

25. The color management method according to claim 24, wherein the color transform of the transform-based color profile is defined by the absolute colorimetric rendering intent.

26. The color management method according to claim 24, wherein the color transform of the transform-based color profile is defined by the media-relative colorimetric rendering intent.

27. The color management method according to claim 22, wherein the color appearance based transform created in the creating step is in a CIECAM97 format.

28. The color management method according to claim 22, wherein the color appearance based transform created in the creating step is in a CIECAM02 format.

29. An apparatus for generating color measurements for use in a measurement-based color management system, the apparatus comprising:

a program memory for storing process steps executable to perform a method according to any of claims 1 to 28; and

a processor for executing the process steps stored in said program memory.

30. Computer-executable process steps stored on a computer readable medium, said computer-executable process steps for generating color measurements for use in a measurement-based color management system, said computer-executable process steps comprising process steps executable to perform a method according to any of claims 1 to 28.

31. A computer-readable medium which stores computer-executable process steps, the computer-executable process steps for generating color measurements for use in a measurement-based color management system, said computer-executable process steps comprising process steps executable to perform a method according to any of claims 1 to 28.