Add more info on the Centore inversion algorithm

[cwickham]

Add link to Centore algorithm and describe when someone may prefer to use it. I.e. why I didn't

@article{doi:10.1002/col.20715,
author = {Centore Paul},
title = {An open‐source inversion algorithm for the Munsell renotation},
journal = {Color Research \& Application},
volume = {37},
number = {6},
pages = {455-464},
keywords = {Munsell, renotation, inverse renotation, open source, algorithm},
doi = {10.1002/col.20715},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/col.20715},
eprint = {https://onlinelibrary.wiley.com/doi/pdf/10.1002/col.20715},
abstract = {Abstract The 1943 Munsell renotation includes a table that converts 2734 Munsell specifications into xyY coordinates, along with a graphical interpolation method and a graphical inversion method, that converts xyY coordinates back into Munsell specifications. This article presents open‐source computer code, running in Matlab or Octave, that both interpolates and inverts the Munsell renotation automatically. The steps in both algorithms are described in detail. Like previous inversion algorithms, it relies on interpolations between entries in the 1943 table. For colours near the MacAdam limits, the inversion also requires extrapolations beyond the 1943 entries. The outputs of the current implementation do not differ significantly from the outputs of other inversion algorithms. The main distinguishing feature of the current algorithm is that both the algorithm and code implementation are publicly available. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;}
}

[cwickham]

A la sRGBtoMunsell() in munsellintrpol

[cwickham]

also note from: https://www.stat.auckland.ac.nz/~paul/Reports/roloc/NBS/roloc-nbs.html

Unfortunately, the R version, the 'munsellinterpol' package (Gama and Centore, 2015), does not appear to work correctly. However, the Python version, the 'colour' package (Mansencal et al., 2017), does work and, with the help of the R package 'reticulate' (Allaire et al., 2017), can be run easily from R.

[glenndavis52]

munsellinterpol now works correctly. version 2.0.1, June 7 2018.
However, the results are not precisely the same as Paul Centore's,
because I wrote a new interpolation method.
I plan to make more improvements and write more vignettes.

Glenn Davis