title: How to calculate the mean IU score in image segmentation?
body: <p>How to compute the <em>mean IU</em> (mean Intersection over Union) score as in <a href="http://www.cs.berkeley.edu/~jonlong/long_shelhamer_fcn.pdf">this</a> paper?</p>
  
  <blockquote>
    <p>Long, Jonathan, Evan Shelhamer, and Trevor Darrell. "Fully Convolutional Networks for Semantic Segmentation."</p>
  </blockquote>