.makeEquivalentMunsellLUT: .makeEquivalentMunsellLUT

Description

Makes the look up table based on pair-wise CIE2000 color contrast (dE00) of LAB colors with D65 illuminant of LAB colors for all whole value/chroma "chips" in the aqp::munsell data set via farver::compare_colour. Specify a threshold in terms of a probability level of CIE2000 distance (relative to whole dataset).

Usage

.makeEquivalentMunsellLUT(threshold = 0.001)

Arguments

threshold

Quantile cutoff (of dE00 color contrast) for "equivalent" colors, default 0.001 based on all whole value/chroma "chips" in the munsell data set.

Value

A list with equal length to the number of rows (chips) in munsell data, each containing a numeric vector of row indices that are equivalent (CIE2000 distance less than threshold).

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 Fran<U+00E7>ois (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

Examples

Run this code

# NOT RUN {
  # use default threshold
  equivalent_chip_lut <- .makeEquivalentMunsellLUT()

  # inspect the first 10 chips, it seems to work!
  lapply(equivalent_chip_lut[1:10], function(i) munsell[i,])

  # lets see some info on the number of chips per chip
  nchipsper <- sapply(equivalent_chip_lut, length)

  # top 10 are very high chroma chips with over 70 chips "identical"
  nchipsper[order(nchipsper, decreasing = TRUE)[1:10]]

  # look at distribution
  plot(density(nchipsper))

  # median is 5 -- Q: is this true of the range of Munsell colors typically used for soils?
  quantile(nchipsper)

  # double the default threshold
  doubletest <- sapply(.makeEquivalentMunsellLUT(threshold = 0.002), length)
  lines(density(doubletest), lty=2)

  # apprx. doubles the number of chips per chip in IQR
  quantile(doubletest)
# }
# NOT RUN {
# }