lass="n">PixelLocatorConcept</span><span class="o">&lt;</span><span class="n">RandomAccess2DLocatorConcept</span> <span class="n">Loc</span><span class="o">&gt;</span>
<span class="p">{</span>
  <span class="n">where</span> <span class="n">PixelValueConcept</span><span class="o">&lt;</span><span class="n">value_type</span><span class="o">&gt;</span><span class="p">;</span>
  <span class="n">where</span> <span class="n">PixelIteratorConcept</span><span class="o">&lt;</span><span class="n">x_iterator</span><s