add a color name library, display it in color picker

[aurelienpierre]

This has been requested by several color-disabled people who wanted to check the color of surfaces to ensure their validity compared to the rest of the population.

We split the visible gamut in 15 hues × 4 lightnesses. Colors are identified coarsely. Colors should have L < 100 % meaning they should be reflective.

We also add average skin tones at ~80% confidence for Kurdish, Chinese, Thai, Caucasian, African-American and Mexican people. The skin tones detection needs proper L scaling, which is 44 to 48 % for African and 58 to 64 % for all others. Of course, neutral white-balance is of the essence here. This is not an ethnicity detection so one skin tone can be detected as belonging to more than one ethnicity, given that skin gamuts overlap greatly between ethnicities (see ref 1 below for graphs).

Reference :

1. XIAO, Kaida, YATES, Julian M., ZARDAWI, Faraedon, et al.
   Characterising the variations in ethnic skin colours: a new calibrated data base for human skin.
   Skin Research and Technology, 2017, vol. 23, no 1, p. 21-29.
   https://onlinelibrary.wiley.com/doi/pdf/10.1111/srt.12295
   Sample : 187 caucasian, 202 chinese, 145 kurdish and 426 thai.

2. DE RIGAL, Jean, DES MAZIS, Isabelle, DIRIDOLLOU, Stephane, et al.
   The effect of age on skin color and color heterogeneity in four ethnic groups.
   Skin Research and Technology, 2010, vol. 16, no 2, p. 168-178.
   https://pubmed.ncbi.nlm.nih.gov/20456097/
   Sample : 121 african-american, 64 mexican.
   Note : the data have been read on the graph and are inaccurate and std is majorated.
   The original authors have been contacted to get the tabulated, accurate data,
   but the main author is retired, co-authors have changed jobs, and the L'Oréal head of R&D
   did not respond. So the values here are given for what it's worth.

[TurboGit]

Seems like there is an issue with all patches without color (white, shade of grey....). See screen shot, I have selected the white patch, it tells me that it is "violet".

For the grey above it tells me it is : "deep sky blue", the RGB values are 163, 167, 169.

[TurboGit]

Issues with white/grey patches.

[aurelienpierre]

The thing is we only read hue and lightness. We don't care about chroma. I could probably add a chroma check for low chroma vs. high chroma, but we already have 60 colors in the lib, I'm reluctant to also discretize chroma to end up with 120 or 240 colors to input.

[TurboGit]

I understand, but this is about helping people working with colors by having the right color name written. If for all color without much chroma we issue a wrong and misleading name I think we fail the initial goal :) So I would either:

• not display a name when there is no chroma detected
• have the code update to take chroma into account

Or any better idea...

[aurelienpierre]

I think outputing "grey" if chroma < threshold is the easiest way for now.

[TurboGit]

@aurelienpierre : I've added the "grey" and I have moved the code into a C file avoid all in header. Merged manually.