Apparatus and process for a digital swatchbook

• US 5,798,943 A
• Filed: 03/28/1997
• Issued: 08/25/1998
• Est. Priority Date: 03/21/1995
• Status: Expired due to Term

• Current Assignee: X-Rite Incorporated (Danaher Corporation)
• Original Assignee: Light Source Computer Images, Inc. (Danaher Corporation)
• Inventors: Cook, Robert L., Herrmann, Eric M., Dirik, Akin, Offner, Nelson, Baca, Lawrence D., Granger, Edward M.
• Primary Examiner(s): Cosimano, Edward R.
• Application Number:
  US08/826,031
• Time in Patent Office: 515 Days
• Field of Search: 356/326, 356/405, 356/408, 364/526, 382/162
• US Class Current: 382/162
• CPC Class Codes: G01J 2003/466 Coded colour; Recognition of predetermined colour; Determining proximity to predetermined colour
• CPC Class Codes: G01J 3/46 Measurement of colour; Colour measuring devices, e.g. colorimeters measuring colour temperature G01J5/60
• CPC Class Codes: G01J 3/462 Computing operations in or between colour spaces; Colour management systems
• CPC Class Codes: G01J 3/463 Colour matching
• CPC Class Codes: G01J 3/465 taking into account the colour perception of the eye; using tristimulus detection

Abstract

The present invention provides a method and apparatus for accurately matching colors. The color matching system includes a host computer and a color input device in communication with the host computer. Preferably the color input device is capable of obtaining spectral data, such as that obtained using a spectrophotometer. The host computer includes a color library, a color management system, a monitor, and a user interface. In one aspect of the invention, the user selects a target color, a color library to use for matching, a color distance tolerance, and a light source under which the colors are to be matched. The target color is compared to the colors in the library and the color or colors in the library that are within the specified color tolerance are reported. In a second aspect of the invention, the user selects a color and two illuminants. The color under each of the two illuminants is compared and the color distance between the two is reported. In a third aspect of the invention, a selected color is transformed to the color space of a designated printer and then back-transformed to the color space of the monitor and displayed. The displayed color represents a simulation of the selected color as it would appear if printed.

Claims

1. In an appropriately programmed digital computer, a method of matching colors comprising the steps of:

acquiring a digital representation of a target color;

choosing a color difference tolerance;

selecting a color library from a plurality of pre-set color libraries, wherein said selected color library contains a plurality of digital color representations;

computing a color difference between said target color and each color of said selected color library;

comparing said color difference for each color of said selected color library to said color difference tolerance; and

providing each color of said color library in which said color difference between said color and said target color is less than said color difference tolerance.

2. The method of claim 1, wherein said plurality of color libraries includes at least one pre-defined color library and at least one user-defined library.

3. The method of claim 1, wherein said acquiring step is performed using a spectrophotometer.

4. The method of claim 1, wherein said acquiring step is performed using a calorimeter.

5. The method of claim 1, wherein said providing step is performed using a monitor.

6. The method of claim 1, further comprising the step of providing a total number of color matches in which the difference between said color and said target color is less than the color difference tolerance.

7. The method of claim 1, wherein said target color and each color of said selected color library is in the form of a spectral data.

8. The method of claim 7, wherein said spectral data is transmittance data.

9. The method of claim 7, wherein said spectral data is reflectance data.

10. The method of claim 9, further comprising the following steps prior to said computing step:

selecting an illuminant spectrum;

adjusting said reflectance data for said target color and for each color of said selected color library to account for said illuminant spectra to produce a plurality of intensity spectra; and

converting each of said intensity spectra to a CIE XYZ color space.

11. The method of claim 1, further comprising the steps of selecting a first illuminant and converting all colors within said selected color library and said target color to a first tristimulus color space based on said first illuminant, said selecting and converting steps occurring prior to said computing step.

12. The method of claim 11, wherein said tristimulus color space is a CIE XYZ color space.

13. The method of claim 11, wherein said tristimulus color space is a perceptually uniform color space.

14. The method of claim 11, wherein said tristimulus color space is a CIE Lab color space.

15. The method of claim 11, further comprising the steps of selecting a second illuminant and converting all colors within said selected color library and said target color from said first tristimulus color space to a second tristimulus color space, said second tristimulus color space based on said second illuminant, said selecting and converting steps occurring prior to said computing step.

16. In an appropriately programmed digital computer, a method of matching colors comprising the steps of:

acquiring a digital representation of a target color;

selecting a color library from a plurality of pre-set color libraries, wherein said selected color library contains a plurality of digital color representations;

computing a color difference between said target color and each color of said selected color library; and

providing a representation of said color from said selected color library having the smallest color difference.

17. In an appropriately programmed digital computer, a method of matching colors comprising the steps of:

acquiring a digital representation of a target color;

selecting a color library from a plurality of pre-set color libraries, wherein said selected color library contains a plurality of digital color representations;

computing a color difference between said target color and each color of said selected color library;

selecting a number of said colors of said color library to be provided;

providing a representation of said number of said colors from said color library having the smallest color differences.

18. A digital computer system for color matching, comprising:

a color sampling device, responsive to input light, for generating a spectral representation of a selected target color;

a first writable memory for storing said spectral representation of said target color, said first writable memory coupled to a processor;

a user interface coupled to said processor, wherein said user interface is capable of communicating a color difference tolerance to said processor;

a plurality of color libraries stored in a second memory, wherein said second memory is non-volatile and coupled to said processor, each color library of said plurality of color libraries containing spectral representations of a plurality of individual colors, wherein one of said plurality of color libraries is selected by said processor, wherein said processor computes a color difference between said target spectral representation and each of said individual color spectral representations of said selected color library and compares each of said computed color differences with said color difference tolerance; and

a display for communicating to a user a representation of each color of said selected color library for which the color difference is less than said color difference tolerance.

19. The digital computer system of claim 18, wherein said selection of said color library by said processor is based on instructions received by said processor from said user interface.

20. The digital computer system of claim 18, wherein said first writable memory and said second memory are the same.

21. In an appropriately programmed digital computer, a method of matching colors comprising the steps of:

acquiring a digital representation of a target color;

choosing a color difference tolerance;

selecting a color library from a plurality of pre-set color libraries, wherein said selected color library contains a plurality of digital color representations;

computing a color difference between said target color and each color of said selected color library;

comparing said color difference for each color of said selected color library to said color difference tolerance;

providing each color of said color library in which said color difference between said color and said target color is less than said color difference tolerance, each provided color defining a match; and

providing a total number of matches.

22. The method of claim 21, wherein said plurality of color libraries includes at least one pre-defined color library and at least one user-defined library.

23. The method of claim 21, further comprising the steps of selecting a first illuminant and converting all colors within said selected color library and said target color to a first tristimulus color space based on said first illuminant, said selecting and converting steps occurring prior to said computing step.

24. The method of claim 21, wherein said tristimulus color space is selected from the group consisting of a CIE XYZ color space, a perceptually uniform color space, and a CIE Lab Color space.