title: How to visualize fhog (not HOG)
body: <p>My MATLAB code uses <code>fhog</code> (instead of Hog) to extract features. However, I want to visualize the HOG features used on the image patch. I know <code>extractHOGFeatures</code> or <a href="http://www.vlfeat.org/overview/hog.html" rel="nofollow noreferrer">VLFeat</a> is used if we use <code>HOG</code> available in MATLAB. But how do I visualize <code>fhog</code>?</p>
  
  <p>Since Piotr's Image &amp; Video Toolbox (which has <code>fhog</code>) is widely used in MATLAB now and I frequently need it, it would be great if someone can tell me how to visualize <code>fhog</code> extracted features.</p>
  
  <p>The code of fhog can be found at <a href="https://pdollar.github.io/toolbox/channels/fhog.html" rel="nofollow noreferrer">here</a>:</p>
  
  <p>The code snippet is as follows:</p>
  
  <pre><code>if features.hog,
      %HOG features, from Piotr's Toolbox
      x = double(fhog(single(im) / 255, cell_size,    features.hog_orientations));
      x(:,:,end) = [];  %remove all-zeros channel ("truncation feature")
  end
  
  if features.gray,
      %gray-level (scalar feature)
      x = double(im) / 255;
  
      x = x - mean(x(:));
  end
  </code></pre>
  
  <p>Edit: <code>hogDraw</code> <a href="https://github.com/pdollar/toolbox/blob/master/channels/hogDraw.m" rel="nofollow noreferrer">exists</a> but writing the following:</p>
  
  <pre><code>V = hogDraw(features, [cell_size], [fhog]);
  </code></pre>
  
  <p>gives me an error :</p>
  
  <pre><code>Not enough input arguments.
  
  Error in fhog (line 70)
  [M,O]=gradientMex('gradientMag',I,0,1);
  </code></pre>