indicates how much to increase the contrast (0 is none; 3 is typical; 20 is pushing it)
indicates where midtones fall in the resultant image (0 is white; 50% is middle-gray; 100% is black). Specify an apsulute number of pixels or an percentage by passing a value between 1 and 0
Increase or decrease image contrast.
The channels to adjust.
Adjusts the contrast of an image channel with a non-linear sigmoidal contrast algorithm. Increases the contrast of the image using a sigmoidal transfer function without saturating highlights or shadows.