class="kt">int</span> <span class="n">_x</span><span class="p">,</span> <span class="n">_width</span><span class="p">;</span>
  <span class="n">Locator</span> <span class="n">_p</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<p>Iterating through the pixels in an image using <code class="docutils literal"><span class="pre">iterator_from_2d</span></code> is slower
than going through all rows and using the x-iterator at each row. This is
because two comparisons are done per iterat