title: Setting a rectangular ROI given a centre pixel value using OpenCV in C++
body: <p>I am am trying to create a rectangular ROI on an image with the location of a certain pixel being the center of the rectangle . 
  How should I go about doing it ? </p>
  
  <pre><code>image= imread("C:\\image.png",1);
  watermark=imread("C:\\watermark.png",0);
  split(image,yuv_channels);
  
  ROI=yuv_channels[0](Rect(100,100,watermark.cols,watermark.rows)); 
  </code></pre>
  
  <p>How should i modify it such that location (100,100) is at the centre of the ROI ? </p>
  
  <p>Thankyou in advance for any help rendered.</p>