title: im.getcolors() returns None
body: <p>I am using a simple code to compare an image to a desktop screenshot through the function getcolors() from PIL. When I open an image, it works:</p>
  
  <pre><code>im = Image.open('sprites\Bowser\BowserOriginal.png')
  current_sprite = im.getcolors() 
  print current_sprite
  </code></pre>
  
  <p>However, using both pyautogui.screenshot() and ImageGrab.grab() for the screenshot, my code returns none. I have tried using the RGB conversion as shown here: <a href="https://stackoverflow.com/questions/27579899/cannot-use-im-getcolors">Cannot use im.getcolors</a>.</p>
  
  <p>Additionally, even when I save a screenshot to a .png, it STILL returns none.</p>
  
  <pre><code>i = pyautogui.screenshot('screenshot.png')
  f = Image.open('screenshot.png')
  im = f.convert('RGB')
  search_image = im.getcolors()
  print search_image
  </code></pre>
  
  <p>First time posting, help is much appreciated.</p>