title: how to transform a OpenCV cvMat back to ndarray in numpy ？
body: <p>I follow the code in OpenCV cookbook for python interface to transform cvMat to numpy array: </p>
  
  <pre><code>mat = cv.CreateMat(3,5,cv.CV_32FC1)
  cv.Set(mat,7)
  a = np.asarray(mat)
  </code></pre>
  
  <p>but with OpenCV 2.1 on my PC, it does not work. The result <strong>a</strong> here is a object array, using <strong>"print a"</strong> does not print all element in <strong>a</strong>, only print <code>&lt;cvmat(type=42424005 rows=3 cols=5 step=20 )&gt;</code>. so how to fully transform a <strong>OpenCV Mat object</strong> to original <strong>numpy.ndarray</strong> object.</p>