Elle Stone and Nicolas Robidoux, can you please also have a
look on this topic? Thank you in advance.
Wow, this was a very elaborate answer ...
Fred Weinhaus also answered me and he is pointing to some transfer
functions that ImageMagick uses, see
He also gives some helpful illustrations what effects different transfer
functions have on the image:
I understand what Elle says in regard to histogram clipping, i.e. max(R,
G, B) being very helpful for finding the white point -- while min (R, G,
B) in regard to the black point is missing.
Perhaps one should give the user just a few more options what to display
in the histogram and how to transfer R, G, B into a single 'value'. I
would be very lucky with 'Rec709Luma' as defined by ImageMagick. I
understand that GIMP internally uses the sRGB colour space at the moment
A standalone feature for GIMP would be the possibility to display a
cumulated histogram, which would for instance demonstrate the effect of
equalisation better than an ordinary histogram. This should be easy to
implement, I guess, and would be a simple check box for the user.
BTW: Besides equalisation, one could also try to meet other cumulative
histogram distribution, like a Gaussian bell curve, see
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