(PECL imagick 2.0.0)
Imagick::contrastImage — Change the contrast of the image
This function is currently not documented; only its argument list is available.
Enhances the intensity differences between the lighter and darker elements of the image. Set sharpen to a value other than 0 to increase the image contrast otherwise the contrast is reduced.
The sharpen value
Returns TRUE on success.
Throws ImagickException on error.