title: PIL / urllib2 - cannot identify image file when passing file using StringIO
body: <p>I'm downloading an image from the web using urllib2. Once I have downloaded it I want to do some stuff with it using an image module called PIL. I don't want to save the file to disk then reopen but rather pass it from memory using <code>StringIO</code></p>
  
  <pre><code>from PIL import Image
  
  image_buff = urllib2.urlopen(url)
  image = Image.open(StringIO.StringIO(image_buff))
  </code></pre>
  
  <p>However when I do this I get the following error </p>
  
  <pre><code>IOError: cannot identify image file &lt;StringIO.StringIO instance at 0x101afa2d8
  </code></pre>
  
  <p>I think this is because I'm not passing a string but rather a urllib2 object/instance. Would anyone know how I can pass a string to PIL correctly. </p>