Adding support for alpha masked images.
Adding support for alpha masked images.

Signed-off-by: Alistair Kearney <e9adbcf81c8a36ccc628e09bc92d0e25e1c8e501@21degrees.com.au>
avanteweb/jit_image_manipulation,DeuxHuitHuit/jit_image_manipulation,avanteweb/jit_image_manipulation,DavidOliver/jit_image_manipulation,DavidOliver/jit_image_manipulation,DeuxHuitHuit/jit_image_manipulation