Changes the brightness and contrast of the alpha channel.
Sets the "brightness" of the alpha channel.
Range from -100% to 100%, default 0% means no change in
brightness.
Higher values mean more opaque, lower values mean more
transparent.
Change the contrast of the alpha channel.
Range from -100% to 100%, default 0% means no change in
contrast.
-100% contrast means the entire alpha channel has the same
transparency, 100% means pixels are either fully opaque or
transparent.