title: convert cv::Mat to const CvMat* or CvMat*
body: <p>I know only <strong>C</strong> language, so I am getting confusion/not understanding the syntax of the <code>openCV</code> data types particularly in <code>cv::Mat, CvMat*, Mat.</code> </p>
  
  <p>My question is How can I convert <code>cv::Mat</code> to <code>const CvMat</code>* or <code>CvMat*</code>, and can any one provide documentation link for difference between  <code>CvMat *mat</code> and <code>cv::Mat</code> and <code>Mat</code> in <strong>opencv2.4</strong>.</p>
  
  <p>and How can I convert my int data to float data in CvMat ?
  Thank you</p>