title: Can't use SURF, SIFT in OpenCV
body: <p>I'm trying a simple thing like</p>
  
  <pre><code>detector = cv2.SIFT()
  </code></pre>
  
  <p>and get this bad error</p>
  
  <pre><code>detector = cv2.SIFT()
  AttributeError: 'module' object has no attribute 'SIFT'
  </code></pre>
  
  <p>I do not understand that because cv2 is installed.</p>
  
  <p><code>cv2.__version__</code> is</p>
  
  <pre><code>$Rev: 4557 $
  </code></pre>
  
  <p>My system is Ubuntu 12.04.</p>
  
  <p>Maybe someone has got the same problem and could help me.</p>
  
  <p><strong>EDIT:</strong></p>
  
  <p>Long story short, <em>testypypypy.py</em>:</p>
  
  <pre><code>import cv2
  
  detector = cv2.SIFT()
  </code></pre>
  
  <p>ERROR:</p>
  
  <pre><code>Traceback (most recent call last):
    File "testypypy.py", line 3, in &lt;module&gt;
      detector = cv2.SIFT()
  AttributeError: 'module' object has no attribute 'SIFT
  </code></pre>
  
  <p>If I take <code>SURF</code> it works because <code>SURF</code> is in <code>dir(cv2)</code> but if I also take <code>cv2.BFMatcher()</code> I get the same error... So it's missing and I have to add it but I don't know how.</p>