'Paste a PIL image into the bitmap image.
:param im: A PIL image.  The size must match the target region.
If the mode does not match, the image is converted to the
mode of the bitmap image.
:param box: A 4-tuple defining the left, upper, right, and
lower pixel coordinate.  If None is given instead of a
tuple, all of the image is assumed.'

def paste(self, im, box=None):

    im.load()
    if (self.mode != im.mode):
        im = im.convert(self.mode)
    if box:
        self.image.paste(im.im, box)
    else:
        self.image.paste(im.im)
