title: How to gauss-filter (blur) a floating point numpy array
body: <p>I have got a numpy array <code>a</code> of type <code>float64</code>.  How can I blur this data with a Gauss filter?</p>
  
  <p>I have tried</p>
  
  <pre><code>from PIL import Image, ImageFilter
  
  image = Image.fromarray(a)
  filtered = image.filter(ImageFilter.GaussianBlur(radius=7))
  </code></pre>
  
  <p>, but this yields <code>ValueError: 'image has wrong mode'</code>. (It has mode <code>F</code>.)</p>
  
  <p>I could create an image of suitable mode by multiplying <code>a</code> with some constant, then rounding to integer. That should work, but I would like to have a more direct way.</p>
  
  <p>(I am using Pillow 2.7.0.)</p>