Thanks. I definitely need some advises for the code.
The parameter delta in the equations can be used to control the midtones bias of the grain. When delta is big enough, for example when it is equal 2, the results are indistinguishable from the old implementation.
In the code, I implemented a midtones_bias parameter to be assigned to a slider. When is it 0, delta is equal to MAX_DELTA (=2) obtaining the same output of the old implementation, and when it is 1, delta is equal to MIN_DELTA (=0.005) obtaining the full midtones bias.
Right now I’m trying to add the slider. 