title: Tune of aruco detection parameters on marker identification
body: <p>I've two photo really similar
  this one is recognized correctly as marker 209 of a 5x5_250 dictionary</p>
  
  <p><a href="https://i.stack.imgur.com/WF1q2.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/WF1q2.jpg" alt="marker 209 recognized by Aruco"></a></p>
  
  <p>while this other really similar it is not recognized,
  it is the marker 207 of the same 5x5_250 dictionary:</p>
  
  <p><a href="https://i.stack.imgur.com/eRt4r.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eRt4r.jpg" alt="marker 207 NOT recognized by Aruco"></a></p>
  
  <p>and also the marker 207 is instead recognized in this other photo:</p>
  
  <p><a href="https://i.stack.imgur.com/gNl2J.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gNl2J.jpg" alt="marker 207 recognized"></a></p>
  
  <p>I've tried changing something in the detector parameters</p>
  
  <pre><code>params-&gt;adaptiveThreshWinSizeMin = 4;
  params-&gt;adaptiveThreshWinSizeMax = 26;
  params-&gt;adaptiveThreshWinSizeStep = 2;
  params-&gt;minMarkerPerimeterRate = 0.01;
  params-&gt;maxMarkerPerimeterRate = 4;
  params-&gt;polygonalApproxAccuracyRate = 0.1;
  params-&gt;perspectiveRemovePixelPerCell = 10;
  </code></pre>
  
  <p>but it seems nothing change so I turn back to the default values, 
  so my question is:</p>
  
  <ol>
  <li>it is necessary a white border surrounding the marker?</li>
  <li>why the marker 207 is not recognized in the second photo?
  Thanks</li>
  </ol>