title: Return value of threshold function in opencv
body: <p>I am applying Otsu threshold method using opencv 2.4.9 function 'threshold'</p>
  
  <p>As per opencv documentation:</p>
  
  <blockquote>
    <p>The special value THRESH_OTSU may be combined with one of the above values. In this case, the function determines the optimal threshold value using the Otsu’s algorithm and uses it instead of the specified thresh . The function returns the computed threshold value. Currently, the Otsu’s method is implemented only for 8-bit images.</p>
  </blockquote>
  
  <p>For my test image function is returning value of 49.</p>
  
  <ol>
  <li>What does 49 signify?</li>
  <li>How can I use it for further thresholding operation like masking rows which are having no of white pixels less than threshold?</li>
  </ol>