title: OpenCV Point(x,y) represent (column,row) or (row,column)
body: <p>I have a 300x200 image in a Matrix <code>src</code>. I am doing the following operation on the image.</p>
  
  <pre><code>for(int i=0;i&lt;src.rows;i++){
    for(int j=0;j&lt;src.cols;j++){
      line( src, Point(i,j),Point(i,j), Scalar( 255, 0, 0 ),  1,8 );
    }
  }
  imshow("A",src);
  waitKey(0);
  </code></pre>
  
  <p>I was expecting it to cover the entire image in white, but lower portion of the image remain empty. While if I do this</p>
  
  <pre><code>  for(int i=0;i&lt;src.rows;i++){
      for(int j=0;j&lt;src.cols;j++){
        src.at&lt;uchar&gt;(i,j)=255;
      }
    }
    imshow("A",src);
    waitKey(0);
  </code></pre>
  
  <p>Entire image is covered in white. So, this means that <code>src.at&lt;uchar&gt;(i,j)</code> is using <code>(i,j)</code> as (row,column) but <code>Point(x,y)</code> is using <code>(x,y)</code> as (column,row)</p>