title: 'tuple' object does not support item assignment
body: <p>I am using the PIL library.</p>
  
  <p>I am trying to make an image look red-er, this is what i've got.</p>
  
  <pre><code>from PIL import Image
  image = Image.open('balloon.jpg')
  pixels = list(image.getdata())
  for pixel in pixels: 
      pixel[0] = pixel[0] + 20    
  image.putdata(pixels)
  image.save('new.bmp')
  </code></pre>
  
  <p>However I get this error: <code>TypeError: 'tuple' object does not support item assignment
  </code></p>