title: Merging cv::Mat horizontally
body: <p>I want to merge a few <code>cv::Mat</code>, when I use <code>mat1.push_back(mat2)</code> it add <code>mat2</code> to the end of <code>mat1</code> vertically , is there a way to do this horizontally?
  The only other option I can think of is making every <code>cv::Mat</code> into a <code>cv::RotatedRect</code>, rotate it, creating a new <code>Mat</code>, merging, rotating everything in the end in the same way, but it sound pointlessly long if there is another way</p>