python PILで透明なベース画像

import Image, ImageFilter, os, glob, random, math

imgWidth = 1280
imgHeight = 960

ground = Image.new( "RGB", ( imgWidth, imgHeight ), ( 0, 0, 0 ) )
ground.putalpha( Image.new( "L", ( imgWidth, imgHeight ), 0 ) )

#ここでgroundの上に画像を乗せていく(ground.paste())
#~~

ground.save( "photoMess.png" )

参考