Create green chroma key image out of RGBA image

gistfile1.py

from PIL import Image
import glob, os

scale = 0.5

for infile in glob.glob( "*.png" ):
    file, ext = os.path.splitext( infile )

    im = Image.open( infile )
    im = im.resize( ( int( im.size[ 0 ] * scale ), int( im.size[ 1 ] * scale ) ) )

    im2 = Image.new( "RGB", im.size, "#00ff00" )
    im2.paste( im, None, im )

    im2.save( file + "_chroma.png", "PNG" )