title: Using Python to Decode Steganography Images (example images at Wikipedia)
body: <p>At <a href="https://en.wikipedia.org/wiki/Steganography#Digital_messages" rel="nofollow">Wikipedia's Steganography Article</a> there is an example image given with hidden image data.</p>
  
  <ul>
  <li><a href="https://en.wikipedia.org/wiki/File:Steganography_original.png" rel="nofollow">Original Image of trees found here</a></li>
  <li><a href="https://en.wikipedia.org/wiki/File:Steganography_recovered.png" rel="nofollow">Decrypted image data of a cat found here</a></li>
  </ul>
  
  <p>Wikipedia notes:</p>
  
  <blockquote>
    <p><a href="https://en.wikipedia.org/wiki/File:Steganography_original.png" rel="nofollow">Image of a tree</a> with a steganographically hidden image. The hidden image is revealed by removing all but the two least significant bits of each color component and a subsequent normalization. The hidden image is shown <a href="https://en.wikipedia.org/wiki/File:Steganography_recovered.png" rel="nofollow">(here)</a>.</p>
  </blockquote>
  
  <p><strong>QUESTION:</strong> I'm confused about "subsequent normalisation"; assuming working Python 2.x code based on PIL module, how does normalisation factor into the retrieval?</p>