 yi = x &lt;&lt; <span class="number">2</span>
      r_out_sum = radiusPlus1 * (pr = pixels[yi])
      g_out_sum = radiusPlus1 * (pg = pixels[yi + <span class="number">1</span>])
      b_out_sum = radiusPlus1 * (pb = pixels[yi + <span class="number">2</span>])

      r_sum += sumFactor * pr
      g_sum += sumFactor * pg
      b_sum += sumFactor * pb

      stack = stackStart

      <span class="keyword">for</span> i <span class="keyword">in</span> [<span class="number">0.</span>..radiusPlus1]
        stack.