title: openCV: Sobel edge detection gives me assertion error
body: <p>I am using python-openCV. When using the Sobel edge detection I get the following assertion error:</p>
  
  <pre><code>src.size() == dst.size() &amp;&amp; src.channels() == dst.channels() &amp;&amp; ((src.depth() == CV_8U &amp;&amp; (dst.depth() == CV_16S || dst.depth() == CV_32F)) || (src.depth() == CV_32F &amp;&amp; dst.depth() == CV_32F))
  </code></pre>
  
  <p>I create the <code>dest</code> using <code>CreateImage()</code> and it has same size and channels as <code>src</code>. Also the depth of both src and dest is IPL_DEPTH_8U. I also tried loading image using <code>LoadImageM()</code> so that the constants are of kind <code>CV_*</code> but that didn't help.</p>
  
  <p>I also happen to find out that <code>IPL_DEPTH_8U == CV_8U</code> is <code>false</code>.</p>