Given parameters alpha and beta, return an RDD of tiles where the sigmoidal contrast operation has been performed on each band of each tile.
Given parameters alpha and beta, return an RDD of tiles where the sigmoidal contrast operation has been performed on each band of each tile.
The approach used is described here: https://www.imagemagick.org/Usage/color_mods/#sigmoidal
The center around-which the stretch is performed (given as a fraction)
The standard deviation in the computation, used to avoid saturating the upper and lower parts of the gamut
An RDD of output tiles