title: GAE: How to get the blob-image height
body: <p>Given is the follwing model on GAE:</p>
  
  <pre><code>avatar = db.BlobProperty()
  </code></pre>
  
  <p>By calling the image instance properties height or width (<a href="http://code.google.com/appengine/docs/python/images/imageclass.html#Image_height" rel="noreferrer">see documentation</a>) with:</p>
  
  <pre><code>height = profile.avatar.height
  </code></pre>
  
  <p>the following error is thrown:</p>
  
  <blockquote>
    <p>AttributeError: 'Blob' object has no attribute 'height'</p>
  </blockquote>
  
  <p>PIL is installed.</p>