Compute the CIE 1974 color rendering index (CRI) of a light spectrum,
called the the test illuminant.
From the given spectrum a reference illuminant is selected with the same CCT (Correlated Color Temperature). A selected set of 8 color samples is rendered in XYZ (1931) with both illuminants and 8 color differences are computed in a special CIEUVW color space. For each color difference a CRI is computed, where 100 is a perfect color match. The final CRI is the average of these 8 CRI values.
an colorSpec R object with
for the CRI to be meaningful the chromaticities of the test and reference illuminants must be sufficiently close in the CIE
1960 uniform chromaticity space.
If the tolerance is exceeded, the function returns
The CCT of
x is computed by
the package minpack.lm is required.
TRUE the 8 test
are chromatically adapted from the test illuminant to the reference illuminant
using a special von Kries type transformation; see Oleari and
The test UVW values are computed relative to the reference illuminant.
FALSE the 8 test
are not chromatically adapted,
and the test UVW values are computed relative to the test illuminant.
computeCRI() returns a single number ≤ 100.
In case of ERROR it returns
TRUE a large list
of intermediate calculations is attached to the returned number.
The test color reflectance spectra are taken from:
Oleari, Claudio, Gabriele Simone. Standard Colorimetry: Definitions, Algorithms and Software. John Wiley. 2016. pp. 465-470.
Günther Wyszecki and W. S. Stiles. Color Science: Concepts and Methods, Quantitative Data and Formulae, Second Edition. John Wiley & Sons, 1982. Table 1(3.11). p. 828.
Wikipedia. Color rendering index. http://en.wikipedia.org/wiki/Color_rendering_index
Hunt, R. W. G. and M. R. Pointer. Measuring Colour. 4th edition. John Wiley & Sons. 2011. Appendix 7.
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