Indeed, the language is a bit disturbing, because it is outside the usual guidelines to which we are accustomed by Adobe, ACES, etc.
You can find the documentation (very incomplete, because I can’t update it) on Rawpedia
GHS - Generalzed hyperbolic stretch
You can also find the documentation made by the author of the algorithm himself (astro - photo).
GHS astro - documentation
I was forced to adapt this algorithm dedicated to astro-photography to extend it to more classic images. In particular, the management of highlights, local contrast, mid-tones and an (essential) adaptation of the notion of White-point and Black-point, which I think will raise a lot of questions (beyond semantics).
And also the discussions on Pixls.us
Discussions
To be a little provocative, the best explanation is in the mathematics used.
Equations
Of course, I remain at your service if you would like to know more.
But, I’m an old Frenchman, I already have a lot of difficulty with English… so for other languages!
I would like to take this opportunity to thank @Lawrence37 for his rigor (I don’t have much of it) in optimizing the code.
Jacques