title: Weird pixel values from OpenCV Mat object
body: <p>I'm trying to extract pixels from an OpenCV <code>Mat</code> object. When I extract them as <code>Vec4b</code>, it works nicely, but when I use a <code>Scalar</code>, which is the standard (afaik), then I get weird numbers. How to use <code>Scalar</code> and interpret the numbers correctly?</p>
  <p>Code for extracting pixel (0, 0), once as <code>Vec4b</code> and once as <code>Scalar</code> (which is in fact a <code>Scalar_&lt;double&gt;</code>):</p>
  <pre><code>cv::Vec4b vec = stroke.at&lt;cv::Vec4b&gt;(0, 0);
  printf(&quot;vec: %i, %i, %i\n&quot;, vec[0], vec[1], vec[2]);
  cv::Scalar sca = stroke.at&lt;cv::Scalar&gt;(0, 0);
  printf(&quot;sca: %5.1f, %5.1f, %5.1f\n&quot;, sca[0], sca[1], sca[2]);
  </code></pre>
  <p>Output:</p>
  <pre><code>vec: 223, 178, 77
  sca: -91331626426359316704088074967484318223735050578187982644502863694523413598032925912253837118690612448172200441235555626964757579094862898778997953403371230682094365379726071857064466448183314663075981261984082516073752896735112503485663679145991425485597914964276617645535969580912538709979773360278601728.0, ...
  </code></pre>
  <p>I'm expecting some creamy yellow color, so I think that the <code>Vec3b</code> is correct.</p>