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1 """ Function for applying watermarks to images.
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2
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3 Original found here:
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4 http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/362879
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5
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6 """
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7
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8 try:
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9 import Image
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10 import ImageEnhance
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11 except ImportError:
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12 try:
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13 from PIL import Image
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14 from PIL import ImageEnhance
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15 except ImportError:
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16 raise ImportError("The Python Imaging Library was not found.")
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17
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18 def reduce_opacity(im, opacity):
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19 """Returns an image with reduced opacity."""
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20 assert opacity >= 0 and opacity <= 1
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21 if im.mode != 'RGBA':
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22 im = im.convert('RGBA')
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23 else:
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24 im = im.copy()
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25 alpha = im.split()[3]
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26 alpha = ImageEnhance.Brightness(alpha).enhance(opacity)
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27 im.putalpha(alpha)
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28 return im
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29
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30 def apply_watermark(im, mark, position, opacity=1):
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31 """Adds a watermark to an image."""
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32 if opacity < 1:
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33 mark = reduce_opacity(mark, opacity)
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34 if im.mode != 'RGBA':
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35 im = im.convert('RGBA')
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36 # create a transparent layer the size of the image and draw the
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37 # watermark in that layer.
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38 layer = Image.new('RGBA', im.size, (0,0,0,0))
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39 if position == 'tile':
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40 for y in range(0, im.size[1], mark.size[1]):
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41 for x in range(0, im.size[0], mark.size[0]):
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42 layer.paste(mark, (x, y))
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43 elif position == 'scale':
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44 # scale, but preserve the aspect ratio
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45 ratio = min(
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46 float(im.size[0]) / mark.size[0], float(im.size[1]) / mark.size[1])
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47 w = int(mark.size[0] * ratio)
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48 h = int(mark.size[1] * ratio)
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49 mark = mark.resize((w, h))
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50 layer.paste(mark, ((im.size[0] - w) / 2, (im.size[1] - h) / 2))
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51 else:
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52 layer.paste(mark, position)
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53 # composite the watermark with the layer
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54 return Image.composite(layer, im, layer)
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55
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56 def test():
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57 im = Image.open('test.png')
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58 mark = Image.open('overlay.png')
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59 watermark(im, mark, 'tile', 0.5).show()
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60 watermark(im, mark, 'scale', 1.0).show()
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61 watermark(im, mark, (100, 100), 0.5).show()
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62
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63 if __name__ == '__main__':
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64 test()
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