A while ago, I played around with detecting skin tones in GMIC. One thing I did was get lots of photos of people and collect sample pixels from their skin. One thing that made it difficult to detect skin was that there was a lot more greenish and blueish tones than I was expecting.
One thing I ended up doing was having a very limited number of high probability skin tones, and then looking around those pixels for likely but less probable tones.
Judging tones on just colour values is very hard.
In any case, here is a PNG of some skin tones I collect from JPEGs. I make no claim as to it’s usfulness.
