  <span class="n">C</span> <span class="o">=</span> <span class="n">_CIE_ILLUMINANTS</span><span class="p">[</span><span class="s1">&#39;C&#39;</span><span class="p">]</span><span class="o">.</span><span class="n">copy</span><span class="p">()</span>
    <span class="n">C</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">vstack</span><span class="p">((</span><span class="n">C</span><span class="p">,</span><span class="n">cie_interp</span><span class="p">(</span