python使用PIL製作浮水印

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():    im = Image.open('test.png')    mark = Image.open('overlay.png')    watermark(im, mark, 'tile', 0.5).show()    watermark(im, mark, 'scale', 1.0).show()    watermark(im, mark, (100, 100), 0.5).show() if __name__ == '__main__':    test()

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