Generation of color measured data from transform-based color profiles

• US 7,483,170 B2
• Filed: 05/05/2004
• Issued: 01/27/2009
• Est. Priority Date: 05/05/2004
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Haikin, John
• Primary Examiner(s): Coles; Edward L
• Assistant Examiner(s): BURLESON, MICHAEL L
• Application Number:
  US10/840,554
• Publication Number:
  US 20050249403A1
• Time in Patent Office: 1,728 Days
• Field of Search: 358/1.9, 358/1.15, 358/2.1, 358/523, 358/538, 358/530, 345/593, 345/594, 345/153, 382/162, 382/167
• US Class Current: 358/1.9
• 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 constructing a device model for a device, wherein the device model is constructed for use in a measurement-based color management system, the method comprising the steps of:

accessing a transform-based color profile for the device which contains a color transform for transforming color data from a device-dependent color space to a colorimetric device-independent color space, wherein the transform-based color profile is designed for use in a transform-based color management system;

computationally generating color measurements for use in the measurement-based color management system by computationally transforming a plurality of predetermined color samples by using the color transform contained in the transform-based color profile; and

constructing the device model for the device by using the computationally generated color measurements, wherein the device model transforms color data from the device-dependent color space to the calorimetric device-independent color space, and wherein the device model is constructed for use in the measurement-based color management system.

2. 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.

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

4. The color management method according to claim 3, 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.

5. The color management method according to claim 4, 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.

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

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

8. The color management method according to claim 3, wherein the color appearance-based transform created in the creating step is in a CIECAM97 format.

9. The color management method according to claim 3, wherein the color appearance-based transform created in the creating step is in a CIECAM02 format.

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

applying a color appearance-based transform to the color measurements.

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

12. The color management method according to claim 11, 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.

13. The color management method according to claim 12, 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.

14. The color management method according to claim 13, 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.

15. The color management method according to claim 14, wherein the color transform of the transform-based color profile is defined by the absolute colorimetric rendering intent.

16. The color management method according to claim 14, wherein the color transform of the transform-based color profile is defined by the media-relative colorimetric rendering intent.

17. The color management method according to claim 14, wherein the supplied device-dependent color samples are converted into a CIEXYZ color space at a D50 luminance having a power of 500 lux.

18. The color management method according to claim 14, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction of 100.0/65535.0.

19. The color management method according to claim 14, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction 120.0/65535.0.

20. The color management method according to claim 14, wherein said scaling step scales the converted device-dependent color samples by a decimal fraction 150.0/65535.0.

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

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

23. The color management method according to claim 13, wherein the creating step further includes, unscaling the generated color measurements.

24. The color management method according to claim 11, 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.

25. The color management method according to claim 24, wherein the n-dimensional lookup table is a three-dimensional lookup table.

26. The color management method according to claim 25, wherein the color appearance based transform created in the creating step is in a CIECAM97 format.

27. The color management method according to claim 25, wherein the color appearance based transform created in the creating step is in a CIECAM02 format.

28. 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 one of claims 1 to 27, or 10 to 3; and

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

29. 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 by a computer to perform a method according to any one of claims 1 to 27, or 10 to 3.

30. The color management method according to claim 24, 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.

31. The color management method according to claim 30, 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.

32. The color management method according to claim 31, wherein the color transform of the transform-based color profile is defined by the absolute colorimetric rendering intent.

33. The color management method according to claim 31, wherein the color transform of the transform-based color profile is defined by the media-relative colorimetric rendering intent.