title: Explanation of cascade.xml in a haar classifier
body: <p>It would be best if someone could explain the numbers/values in the cascade.xml entirely.
  Example in:</p>
  
  <pre><code>&lt;!-- stage 0 --&gt;
  &lt;_&gt;
    &lt;maxWeakCount&gt;3&lt;/maxWeakCount&gt;
    &lt;stageThreshold&gt;-8.8384145498275757e-001&lt;/stageThreshold&gt;
    &lt;weakClassifiers&gt;
      &lt;_&gt;
        &lt;internalNodes&gt;
          0 -1 66 5.1593100652098656e-003&lt;/internalNodes&gt;
        &lt;leafValues&gt;
          -8.0555558204650879e-001 8.0694979429244995e-001&lt;/leafValues&gt;&lt;/_&gt;
      &lt;_&gt;
        &lt;internalNodes&gt;
          0 -1 108 1.5044789761304855e-002&lt;/internalNodes&gt;
        &lt;leafValues&gt;
          -6.2940740585327148e-001 7.5122624635696411e-001&lt;/leafValues&gt;&lt;/_&gt;
      &lt;_&gt;
        &lt;internalNodes&gt;
          0 -1 99 -4.7172707127174363e-005&lt;/internalNodes&gt;
        &lt;leafValues&gt;
          5.5112153291702271e-001 -8.6111217737197876e-001&lt;/leafValues&gt;&lt;/_&gt;&lt;/weakClassifiers&gt;&lt;/_&gt;
  </code></pre>
  
  <p>What are the meanings of these values</p>
  
  <pre><code>      &lt;internalNodes&gt;
          0 -1 99 -4.7172707127174363e-005&lt;/internalNodes&gt;
  </code></pre>
  
  <p>Another question is, how does the program know which feature to use for a particular stage?
  As far as I know, features are in the form as below</p>
  
  <pre><code>&lt;_&gt;
    &lt;rects&gt;
      &lt;_&gt;
        21 6 3 5 -1.&lt;/_&gt;
      &lt;_&gt;
        22 6 1 5 3.&lt;/_&gt;&lt;/rects&gt;
    &lt;tilted&gt;0&lt;/tilted&gt;&lt;/_&gt;
  </code></pre>
  
  <p>Whereby it's the coordinates of two rectangles, forming something like below:</p>
  
  <pre><code>=-=    = Black colored rectangle
  =-=    - White colored rectangle
  =-=
  =-=
  =-=
  </code></pre>
  
  <p>What are the values -1. and 3. mean? I know it's weights but how is it used to calculate the feature?</p>
  
  <p><strong>Summary</strong></p>
  
  <ol>
  <li>What are the meaning of the values inside <code>&lt;internalNodes&gt;</code>?</li>
  <li>How is the feature calculated? How are the weights in <code>&lt;rects&gt;</code> use?</li>
  <li>Most importantly, which field denotes that which features are being used in a particular stage/node.</li>
  </ol>
  
  <p>Thanks!</p>