title: How to use Mikolajczyk's evaluation framework for feature detectors/descriptors?
body: <p>I'm trying the assess the correctness of my SURF descriptor implementation with the de facto standard <a href="http://www.robots.ox.ac.uk/~vgg/research/affine/" rel="nofollow noreferrer">framework by Mikolajczyk et. al</a>. I'm using OpenCV to detect and describe SURF features, and use the same feature positions as input to my descriptor implementation.</p>
  
  <p>To evaluate descriptor performance, the framework requires to evaluate detector repeatability first. Unfortunately, the repeatability test expects a list of feature positions along with ellipse parameters defining the size and orientation of an image region around each feature. However, OpenCV's SURF detector only provides feature position, scale and orientation.</p>
  
  <p>The <a href="http://www.robots.ox.ac.uk/~vgg/research/affine/det_eval_files/vibes_ijcv2004.pdf" rel="nofollow noreferrer">related paper</a> proposes to compute those ellipse parameters iteratively from the eigenvalues of the second moment matrix. Is this the only way? As far as I can see, this would require some fiddling with OpenCV. Is there no way to compute those ellipse parameters afterwards (e.g. in Matlab) from the feature list and the input image?</p>
  
  <p>Has anyone ever worked with this framework and could assist me with some insights or pointers?</p>