title: Mark the difference between 2 pictures in Python
body: <p>I have recently started to play with Pillow. I am comparing two pictures in Python 3.3 and want to save the difference as an image. </p>
  
  <pre><code>from PIL import Image
  from PIL import ImageChops
  from PIL import ImageDraw
  
  file1 = '300.jpg'
  file2 = '300.jpg'
  
  im1 = Image.open(file1)
  im2 = Image.open(file2)
  
  diff = ImageChops.difference(im1, im2).getbbox()
  draw = ImageDraw.Draw(im2)
  draw.rectangle(diff)
  im2.convert('RGB').save('file3.jpg')
  </code></pre>
  
  <p>But I always get a <strong>TypeError: argument must be sequence</strong></p>
  
  <p>I believe this happens at <strong>draw.rectangle(diff)</strong>
  How can I get rid of the error? </p>
  
  <p>Thank you.</p>