title: How to convert cv::Mat type from CV_16UC1 to CV_8UC1
body: <p>I have a cv::Mat image of type CV_16UC1 and I need it in CV_8UC1, so I can run cv::integral on it. I am not worried about overflow during the conversion - essentially I just want to bulk convert the image from unsigned short to unsigned char.</p>
  
  <p>I asked elsewhere and someone suggested <a href="http://docs.opencv.org/modules/imgproc/doc/miscellaneous_transformations.html#cvtcolor" rel="noreferrer">cvtColor</a>, but I don't know what conversion code to use.</p>