The texture's Contrast can be adjusted with this function. It automatically detects the medium value of the image, which will be used as contrast adjusting pivot.

To raise the contrast, the distance of all the texture's colors to the pivot must be increased. Set the Amplify parameter to a value greater than 100 to perform this operation (Image 3). Values between -100 to 100 make the contrast to be lowered (Image 2), while negative parameters result in an inverted image.