title: getbbox method from python image library (PIL) not working
body: <p>I want to crop an image to its smaller size, by cutting the white areas on the borders. I tried the solution suggested in this forum <a href="https://stackoverflow.com/questions/1905421/crop-a-png-image-to-its-minimum-size">Crop a PNG image to its minimum size</a> but the getbbox() method of pil is returning a bounding box of the same size of the image, i.e., it seems that it doesn't recognize the blank areas around. I tried the following:</p>
  
  <pre><code>&gt;&gt;&gt;import Image
  &gt;&gt;&gt;im=Image.open("myfile.png")
  &gt;&gt;&gt;print im.format, im.size, im.mode
  &gt;&gt;&gt;print im.getbbox()
  PNG (2400,1800) RGBA
  (0,0,2400,1800)
  </code></pre>
  
  <p>I checked that my image has truly white croppable borders by cropping the image with the GIMP auto-crop. I also tried with ps and eps versions of the figure, without luck.<br>
  Any help would be highly appreciated.</p>