Non-von-Kries 3-Parameter Color Prediction
Funt, B., Jiang, Hao,
Non-von-Kries 3-Parameter Color Prediction,
Proc. of SPIE Vol. 5007 Human Vision and Electronic Imaging VIII, Santa Clara, Jan. 2003.
Chromatic adaptation transforms generally rely on a variant of the von
Kries transformation method to account for changes in the LMS cone
signals that occur when changing from one illuminant to another. Von
Kries adaptation—also often referred to as the coefficient rule method
or the diagonal transformation method—adjusts the 3 color channels by
independent scale factors. Since there generally are only 3 known
quantities available, namely the ratio of the cone signals of the two
adapting illuminants, a crucial aspect of the von Kries method is that
it requires only 3 parameters to be specified. A 9-parameter, 3x3 matrix
transformation would be more accurate, but it is generally not possible
to determine the extra parameters. This paper presents a novel method
of predicting the effect a change of illumination has on the cone
signals, while still relying on only 3 parameters. To begin, we create
a large set of 3x3 matrices representing illuminant changes based on a
sizable database of typical illuminant spectra and surface spectral
reflectances. Representing these 3x3 matrices as points in a 9-
dimensional space, we then apply principal components analysis to find a
3-dimensional basis which best approximates the original matrix space.
To model an illumination change, a 3x3 matrix is constructed using a
weighted combination of the 3 basis matrices. The relative weights can
be calculated based on the 3 standard cone ratios obtained from the
illuminant pair. Tests show that the new method yields better results
than von Kries adaptation with or without sensor sharpening.
Full text (pdf, 194KB)
Keywords: Chromatic adaptation, color correction, von Kries, spectral sharpening, color prediction.
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