Method and system for matching a surface color

• US 6,628,829 B1
• Filed: 08/08/2000
• Issued: 09/30/2003
• Est. Priority Date: 08/08/2000
• Status: Expired due to Fees

• Current Assignee: Richard Jeffrey Chasen
• Original Assignee: Richard Jeffrey Chasen
• Inventors: Chasen, Richard Jeffrey
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): SHERALI, ISHRAT I
• Application Number:
  US09/633,933
• Time in Patent Office: 1,148 Days
• Field of Search: 382/165, 382/162, 382/167, 382/100, 382/305, 382/274, 358/504, 358/518, 358/520, 702/104, 702/32, 707/1-6, 707/140.1, 705/500, 356/402-425, 355/40, 433/29, 433/26, 433/215, 345/600, 345/595, 345/603, 700/224-226
• US Class Current: 382/167
• CPC Class Codes: G01J 2003/467 Colour computing
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/463 Colour matching
• CPC Class Codes: G01J 3/52 using colour charts
• CPC Class Codes: G01J 3/524 Calibration of colorimeters
• CPC Class Codes: G06T 11/001 Texturing; Colouring; Generation of texture or colour inpainting G06T5/77
• CPC Class Codes: H04N 1/6033 using test pattern analysis H04N1/6055 takes precedence
• CPC Class Codes: H04N 1/6086 by scene illuminant, i.e. conditions at the time of picture capture, e.g. flash, optical filter used, evening, cloud, daylight, artificial lighting, white point measurement, colour temperature

Abstract

A method for matching a color of a target surface involves capturing a digital image of the target surface and a test card having a pattern of color fields, each color field having a known true color. The digital image is analyzed to determine the captured target color and the captured colors of the of the test card color fields. A correction model accounting for ambient lighting conditions and distortions due to the image capturing device is computed from the captured and known colors of the test card color fields. The correction model is applied to the captured target color and the resulting estimated true target color is compared to a database of true product colors to determine a nearest matching product color.

Claims

1. A method for matching a color of a target surface comprising the steps of:

providing a test card having a pattern of at least one color field printed thereon, each of the at least one color field being monochromatic and having a true color;

positioning the test card adjacent the target surface;

producing a digital record that includes a digital image of the test card and at least a portion of the target surface exhibiting the target surface color, the target surface color producing a captured target color on the digital image and each of the at least one color field producing a captured pattern color on the digital image;

determining an estimated true target color using the captured pattern color and the true color of each of the at least one color field;

providing a database of product color information; and

determining a nearest matching product color using the estimated true target color and the database of product color information.

2. A method for matching a color of a target surface according to claim 1 wherein the step of determining an estimated true target color includes:

determining a set of captured pattern color components for the captured pattern color of each of the at least one color field;

building a correction model having a set of empirical equations derived from the true color and the set of captured pattern color components of each of the at least one color field;

determining a set of captured target color components for the captured target color; and

applying the correction model to the captured target color components to obtain the estimated true target color.

3. A method for matching a color of a target surface according to claim 2 wherein the step of determining an estimated true target color further includes:

determining the location and orientation within the digital record of the digital image of the test card and the at least a portion of the target surface exhibiting the target surface color; and

locating within the digital image the captured pattern color of each of the at least one color field and the captured target color.

4. A method for matching a color of a target surface according to claim 3 further including the step of loading the digital record into a data processing system and wherein the step of determining an estimated true target color is accomplished by the data processing system.

5. A method for matching a color of a target surface according to claim 4 wherein the data processing system includes a central data processor operatively connected to a data entry processor and the step of loading the digital record into the data processing system includes:

loading the digital record into the data entry processor; and

transferring the digital record to the central data processor.

6. A method for matching a color of a target surface according to claim 5 wherein the central data processor and the data entry processor are connected through a network.

7. A method for matching a color of a target surface according to claim 5 wherein the central data processor and the data entry processor are connected through the Internet.

8. A method for matching a color of a target surface according to claim 4 wherein the test card includes an identification code printed thereon, the method further comprising the steps of:

obtaining spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field;

deriving a set of true color components of the at least one color field from the spectral data; and

storing the set of true color components in association with the identification code of the test card, whereby the set of true color components may be selectively retrieved.

9. A method for matching a color of a target surface according to claim 8 wherein the step of determining an estimated true target color includes:

retrieving the set of true color components of each of the at least one color field for use in constructing the correction model.

10. A method for matching a color of a target surface according to claim 4 wherein the test card is one of a batch of test cards and the test card includes an identification code printed thereon, the method further comprising the steps of:

obtaining from a sample subset of the batch of test cards spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field;

deriving a representative set of true color components of each of the at least one color field for the test card from the spectral data of the at least one color field of each of the sample subset of the batch of test cards; and

storing the representative set of true color components in association with the identification code of the test card, whereby the representative set of true color components may be selectively retrieved.

11. A method for matching a color of a target surface according to claim 10 wherein the step of determining an estimated true target color includes:

retrieving the representative set of true color components of each of the at least one color field for use in constructing the correction model.

12. A method for matching a color of a target surface according to claim 1 wherein the test card includes a gray scale having at least one gray field, each of the at least one of gray field having a known relative brightness, and wherein each of the at least one gray field produces an associated captured gray field on the digital image of the test card and the at least a portion of the target surface, the method further comprising the steps of:

determining an overall brightness of the digital image from the known relative brightness and the captured brightness for each captured gray field; and

determining whether the overall brightness is within a set of predetermined brightness limits.

13. A method for matching a color of a target surface according to claim 1 wherein the test card includes a gloss black field that produces an associated captured gloss black field on the digital image of the test card and the at least a portion of the target surface, the method further comprising the steps of:

determining a gloss black brightness level for the captured gloss black color field;

determining a glare level based on the gloss black brightness level; and

determining whether the glare level is within a set of predetermined glare limits.

14. A method for matching a color of a target surface according to claim 1 wherein the database of product color information includes a compilation of true product colors and the step of determining a nearest matching product color includes:

comparing the estimated true target color to at least a portion of the compilation of true product colors; and

selecting the nearest matching product color from the at least a portion of the true product colors.

15. A method for matching a color of a target surface according to claim 1 wherein the database of product color information includes a product color formula whereby a formulation for a colorant product can be determined for a given true color and the step of determining a nearest matching product color includes:

calculating a target color colorant formulation using the product color formula and using the estimated true target color as the given true color, the target color colorant formulation being usable to provide the nearest matching product color.

16. A method for matching a color of a target surface comprising the steps of:

providing a test card having a pattern of at least one color field printed thereon, each of the at least one color field being monochromatic and having a true color;

positioning the test card adjacent the target surface;

producing a digital record that includes a digital image of the test card and at least a portion of the target surface exhibiting the target surface color, the target surface color producing a captured target color on the digital image and each of the at least one color field producing a captured pattern color on the digital image;

providing a data processing system including a user processor operatively connected to a central processor, the central processor having analysis software for analyzing the digital record;

downloading the digital record into the user processor;

transferring the digital record to the central processor;

determining an estimated true target color using the central processor and the analysis software;

comparing the estimated true target color with known true product colors to identify products whose true color matches the estimated true target color within a predetermined set of matching criteria;

transmitting information relating to matching color products to the user processor; and

outputting the information relating to matching color products.

17. A method for matching a color of a target surface according to claim 16 wherein the step of determining an estimated true target color includes:

determining the location and orientation within the digital record of the digital image of the test card and the at least a portion of the target surface exhibiting the target surface color; and

locating within the digital image the captured pattern color of each of the at least one color field and the captured target color;

determining a set of captured pattern color components for the captured pattern color of each of the at least one color field;

building a correction model having a set of empirical equations derived from the true color and the set of captured pattern color components of each of the at least one color field;

determining a set of captured target color components for the captured target color; and

applying the correction model to the captured target color components to obtain the estimated true target color.

18. A method for matching a color of a target surface according to claim 17 wherein the test card includes an identification code printed thereon, the method further comprising the steps of:

obtaining spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field;

deriving a set of true color components of the at least one color field from the spectral data; and

storing the set of true color components in association with the identification code of the test card, whereby the set of true color components may be selectively retrieved.

19. A method for matching a color of a target surface according to claim 18 wherein the step of determining an estimated true target color includes:

retrieving the set of true color components of each of the at least one color field for use in constructing the correction model.

20. A method for matching a color of a target surface according to claim 17 wherein the test card is one of a batch of test cards and the test card includes an identification code printed thereon, the method further comprising the steps of:

obtaining from a sample subset of the batch of test cards spectral data for each of the at least one color field of the test card under lighting conditions configured to establish the true color of the at least one color field;

deriving a representative set of true color components of each of the at least one color field for the test card from the spectral data of the at least one color field of each of the sample subset of the batch of test cards; and

storing the representative set of true color components in association with the identification code of the test card, whereby the representative set of true color components may be selectively retrieved.

21. A method for matching a color of a target surface according to claim 20 wherein the step of determining an estimated true target color includes:

retrieving the representative set of true color components of each of the at least one color field for use in constructing the correction model.

22. A method for matching a color of a target surface according to claim 16 wherein the steps of determining an estimated true target color, comparing the estimated true target color, transmitting information and outputting the information are provided as a service to a user who has purchased the test card, wherein the purchase of the test card entitles the user to a predetermined number of uses of the service.

23. A method for matching a color of a target surface according to claim 22 further comprising the steps of:

determining a number of authorized service uses associated with the test card; and

terminating the service and returning an error message to the user processor if the number of authorized service uses is not greater than zero.

24. A system for matching a color of a target surface using a digital imaging device, the system comprising:

a thin, generally planar test card for placement adjacent the target surface, the test card having an upper surface with a pattern of at least one color field printed thereon, each of the at least one color field being monochromatic and having a true color, the test card being configured so that a digital record of the test card and at least a portion of the target surface exhibiting the target surface color may be obtained using the digital imaging device, the digital record including a digital image of the test card and the target surface color, the target surface color producing a captured target color on the digital image and each of the at least one color field producing a captured pattern color on the digital image;

a data processing system having means for receiving the digital record;

software installed in the data processing system and configured for analysis of the digital record and determination of an estimated true target color by application of a correction model to the captured target color, the correction model being determinable from the true color and the captured pattern color of each of the at least one color field;

and a color product database accessible by the data processing system, the color product database including information from which a nearest matching product color to the estimated true target color may be determined.

25. A system for matching a target color according to claim 24 wherein the data processing system includes a data entry processor operatively connected to a central processor, the software and the color product database being installed in the central processor.

26. A system for matching a target color according to claim 25 wherein the data entry processor and the central processor are connected through a network.

27. A system for matching a target color according to claim 25 wherein the data entry processor and the central processor are connected through the Internet.

28. A system for matching a target color according to claim 24 wherein the test card includes an identification code printed thereon.

29. A system for matching a target color according to claim 28 wherein the test card is one of a plurality of test cards, each having a unique identification code and wherein the system further comprises a database of true color components of the at least one color field for each of the plurality of test cards, the database of true color components being searchable by the identification code, whereby the true color components of the at least one color field of a selected one of the plurality of test cards is accessible to the software.

30. A system for matching a color of a target surface according to claim 24 wherein the test card has an aperture formed therethrough whereby the target surface color may be made visible through the aperture when the test card is placed adjacent the target surface.

31. A system for matching a color of a target surface according to claim 24 wherein a gray scale is printed on the upper surface of the test card, the gray scale including at least one gray field, each of the at least one gray field having a different relative brightness value, the gray scale being configured to produce in the digital image a corresponding captured gray scale from which an overall brightness of the digital image can be ascertained.

32. A system for matching a color of a target surface according to claim 24 wherein a gloss black field is printed on the upper surface of the test card, the gloss black field being configured to produce in the digital image a corresponding captured gloss black field from which a relative glare amount can be ascertained for the digital image.

33. A color test card for use in a system for matching a color of a target surface using a digital imaging device, the color test card comprising:

a thin, generally planar card member having an upper surface and a lower surface;

a pattern of at least one color field printed on the upper surface of the card member, each of the at least one color field being monochromatic and having a true color;

an identification code printed on at least one of the upper and lower surfaces;

a gray scale printed on the upper surface of the test card, the gray scale including at least one gray field, each of the at least one gray field having a different relative brightness value; and

a gloss black field printed on the upper surface of the test card;

wherein the test card is configured so that a digital record of the test card and at least a portion of the target surface exhibiting the target surface color may be obtained using the digital imaging device, the digital record including a digital image of the test card and the target surface color, the target surface color producing a captured target color on the digital image and each of the at least one color field producing a captured pattern color on the digital image.

34. A color test card according to claim 33 wherein the generally planar card member has a predetermined shape configured to facilitate automated location of the digital image of the test card and the target surface color in the digital record using object recognition software.

35. A color test card according to claim 33 wherein the generally planar card member has an aperture formed therethrough whereby the target surface color may be made visible through the aperture when the test card is placed adjacent the target surface.