A pre-calculated lookup list (made with farver::compare_colour) based on pair-wise color contrast (CIE2000 or dE00) evaluated over all "chips" in the aqp::munsell data set.

The intention is to identify Munsell chips that may be "functionally equivalent" to some other given whole chip elsewhere in the Munsell color space -- as discretized in the aqp::munsell lookup table.

"Equivalent" chips are based (fairly arbitrarily) on the 0.001 probability level of dE00 (default Type 7 quantile) within the upper triangle of the 8467x8467 contrast matrix. This corresponds to a dE00 threshold of approximately 2.15.

This is a naive (to the subtleties of human color perception, and overall magnitude of contrast between some of the "chips") but computationally consistent approach. Using the lookup list, as opposed to manual contrast via e.g. farver::compare_colour may have some benefits for efficiency in certain applications where the exact contrast value is not as important as the concept of having some threshold that is non-zero, but very small.

data(equivalent_munsell)

## Format

A named list with 8467 elements, each containing a numeric vector of indices corresponding to the munsell data set, which has 8467 rows (unique, whole-number chips). Names have the format HUE VALUE/CHROMA, e.g. "7.5YR 4/4"

## References

Gaurav Sharma, Wencheng Wu, Edul N. Dalal. (2005). The CIEDE2000 Color-Difference Formula: Implementation Notes, Supplementary Test Data, and Mathematical Observations. COLOR research and application. 30(1):21-30. http://www2.ece.rochester.edu/~gsharma/ciede2000/ciede2000noteCRNA.pdf

Thomas Lin Pedersen, Berendea Nicolae and Romain Francois (2020). farver: High Performance Colour Space Manipulation. R package version 2.0.3. https://CRAN.R-project.org/package=farver

Dong, C.E., Webb, J.B., Bottrell, M.C., Saginor, I., Lee, B.D. and Stern, L.A. (2020). Strengths, Limitations, and Recommendations for Instrumental Color Measurement in Forensic Soil Characterization. J Forensic Sci, 65: 438-449. https://doi.org/10.1111/1556-4029.14193

equivalentMunsellChips
data(equivalent_munsell)