ection.
  </span>
 </div>
</div>

<p>The method used is the same as the one proposed by D. Lowe: the
orientation is given by the dominant gradient direction. Intuitively,
this means that, in the normalized frame, brighter stuff should appear
on the right, or that there should be a left-to-right dark-to-bright
pattern.</p>

<p>In practice, this method may result in an ambiguous detection of
the orientations; in this case, up to four different orientations may
be assigned to the same frame, resulting in a mul