# generate a true opaque watermark with the Python Image Library (PIL)
# free download from: http://www.pythonware.com/products/pil/
 
from PIL import Image, ImageEnhance
 
def reduce_opacity(im, opacity):
    """returns an image with reduced opacity"""
    assert opacity >= 0 and opacity <= 1
    if im.mode != 'RGBA':
        im = im.convert('RGBA')
    else:
        im = im.copy()
    alpha = im.split()[3]
    alpha = ImageEnhance.Brightness(alpha).enhance(opacity)
    im.putalpha(alpha)
    return im
 
def watermark(im, mark, position, opacity=1):
    """adds a watermark to an image"""
    if opacity < 1:
        mark = reduce_opacity(mark, opacity)
    if im.mode != 'RGBA':
        im = im.convert('RGBA')
    # create a transparent layer the size of the image and draw the
    # watermark in that layer.
    layer = Image.new('RGBA', im.size, (0,0,0,0))
    if position == 'tile':
        for y in range(0, im.size[1], mark.size[1]):
            for x in range(0, im.size[0], mark.size[0]):
                layer.paste(mark, (x, y))
    elif position == 'scale':
        # scale, but preserve the aspect ratio
        ratio = min(
            float(im.size[0]) / mark.size[0], float(im.size[1]) / mark.size[1])
        w = int(mark.size[0] * ratio)
        h = int(mark.size[1] * ratio)
        mark = mark.resize((w, h))
        layer.paste(mark, ((im.size[0] - w) / 2, (im.size[1] - h) / 2))
    else:
        layer.paste(mark, position)
    # composite the watermark with the layer
    return Image.composite(layer, im, layer)
 
def test():
    # pick images you have ...
    im = Image.open('Audi.jpg')
    mark = Image.open('Audi2.jpg')
    watermark(im, mark, 'tile', 0.3).show()
    # also try these ...
    #watermark(im, mark, 'scale', 0.3).show()
    #watermark(im, mark, (10, 10), 0.5).show()
 
if __name__ == '__main__':
    test()