n><span class="n">above</span><span class="p">]</span><span class="o">+</span><span class="n">loc</span><span class="p">[</span><span class="n">below</span><span class="p">])</span><span class="o">/</span><span class="mi">2</span><span class="p">;</span>  <span class="c1">// the same, but faster using cached relative neighbor locations</span>
</pre></div>
</div>
<p>The standard GIL locators are fast and lightweight objects. For example, the
locator for a simple interleaved image consists of one raw pointer 