Method and apparatus for use of an universal color index (UCI): a color appearance system calibrated to reflectance spectra
First Claim
1. A method for transforming a physically-based characterization of color defined in Euclidean space derived from reflectance spectra and a theoretically defined perceptual space of color appearance defined in Euclidean space in terms of equal perceptual spacing of human judgments of colors comprising:
- obtaining a physical reflectance spectrum in a selected spectral range of a reflected color of an object;
generating a cube root reflectance spectrum of the physical reflectance spectrum;
reconstructing the cube root reflectance spectrum by a weighted linear combination of three basis functions, the weights of a linear combination of the basis functions constituting coordinates in a physical Euclidean color space with respect to which Euclidean color space similarities and differences between the physical reflectance spectra and a color characterized in the perceptual space of color appearance can be quantitatively analyzed; and
linearly transforming a quantitative characterization of a target color between the physical Euclidean color space and the perceptual space of color appearance by which transformation the target color can be quantitatively compared.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for establishing a relationship between a physical structure of reflectance spectra as defined in a Euclidean color space and a perceptual space of color appearance defined in terms of human perception of colors is performed by obtaining a cube root spectrum of the physical reflectance spectrum in a selected spectral range, reconstructing the cube root of the physical reflectance spectrum by a weighted linear combination of three basis functions, the weights of the linear combination of the basis functions constituting the coordinates in a three-dimensional Euclidean color space with respect to which similarities and differences among reflectance spectra in metric terms and a color characterized in a perceptual space of color appearance can be analyzed, and making an analytic comparison between a physical system in the three-dimensional Euclidean color space and the perceptual system by means of a linear transformation therebetween.
-
Citations
24 Claims
-
1. A method for transforming a physically-based characterization of color defined in Euclidean space derived from reflectance spectra and a theoretically defined perceptual space of color appearance defined in Euclidean space in terms of equal perceptual spacing of human judgments of colors comprising:
-
obtaining a physical reflectance spectrum in a selected spectral range of a reflected color of an object; generating a cube root reflectance spectrum of the physical reflectance spectrum; reconstructing the cube root reflectance spectrum by a weighted linear combination of three basis functions, the weights of a linear combination of the basis functions constituting coordinates in a physical Euclidean color space with respect to which Euclidean color space similarities and differences between the physical reflectance spectra and a color characterized in the perceptual space of color appearance can be quantitatively analyzed; and linearly transforming a quantitative characterization of a target color between the physical Euclidean color space and the perceptual space of color appearance by which transformation the target color can be quantitatively compared. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. An apparatus utilizing a physical structure of a spectrum as defined in the Euclidean color space and a perceptual space of color appearance defined in terms of human perception of colors comprising:
-
a spectrum analyzer to measure a reflectance spectrum from an object in a selected spectral range; a processor coupled to the spectrum analyzer to process data to generate cube root spectrum of the reflectance spectrum in at least a portion of the selected spectral range, to reconstruct the cube root of the physical reflectance spectrum by a weighted linear combination of three basis functions, the weights of the linear combination of the basis functions constituting the coordinates in a three-dimensional Euclidean color space with respect to which similarities and differences among reflectance spectra in metric terms and a color characterized in a perceptual space of color appearance can be characterized, and linearly transforming a quantitative characterization of a target color between the physical Euclidean color space and the perceptual space of color appearance. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. A non-transitory computer-readable storage medium with an executable program stored thereon, wherein the program instructs a microprocessor to perform the following steps:
-
obtaining a physical reflectance spectrum in a selected spectral range of a reflected color of an object; generating a cube root reflectance spectrum of the physical reflectance spectrum; reconstructing the cube root reflectance spectrum by a weighted linear combination of three basis functions, the weights of a linear combination of the basis functions constituting coordinates in a physical Euclidean color space with respect to which Euclidean color space similarities and differences between the physical reflectance spectra and a color characterized in the perceptual space of color appearance can be quantitatively analyzed; and linearly transforming a quantitative characterization of a target color between the physical Euclidean color space and the perceptual space of color appearance by which transformation the target color can be quantitatively compared.
-
-
24. A non-transitory computer-readable storage medium with an executable program stored thereon, wherein the program instructs a microprocessor to process data to generate a cube root spectrum of a reflectance spectrum in at least a portion of a selected spectral range, to reconstruct the cube root of the physical reflectance spectrum by a weighted linear combination of three basis functions, the weights of the linear combination of the basis functions constituting the coordinates in a three-dimensional Euclidean color space with respect to which similarities and differences among reflectance spectra in metric terms and a color characterized in a perceptual space of color appearance can be characterized, and linearly transforming a quantitative characterization of a target color between the physical Euclidean color space and the perceptual space of color appearance.
Specification