Convert QPixmap to Numpy
<p>To convert numpy matrix to QPixmap, I use this function:</p>

<pre><code>def np2qpixmap(np_img):
    frame = cv2.cvtColor(np_img, cv2.COLOR_BGR2RGB)
    img = QtGui.QImage(frame, frame.shape[1], frame.shape[0], QtGui.QImage.Format_RGB888)
    return QtGui.QPixmap.fromImage(img)
</code></pre>

<p>Now how to do the inverse operation ?</p>