mask package:cairo

mask :: Pattern -> Render ()
cairo Graphics.Rendering.Cairo
A drawing operator that paints the current source using the alpha channel of pattern as a mask. (Opaque areas of mask are painted with the source, transparent areas are not painted.)
maskSurface :: Surface -> Double -> Double -> Render ()
cairo Graphics.Rendering.Cairo
A drawing operator that paints the current source using the alpha channel of surface as a mask. (Opaque areas of surface are painted with the source, transparent areas are not painted.)