span class="o">=</span> <span class="n">cb</span><span class="o">*</span><span class="n">b</span>

            <span class="c1"># calculate colorfullness like signal M:</span>
            <span class="n">M</span> <span class="o">=</span> <span class="n">cM</span><span class="o">*</span><span class="p">((</span><span class="n">a</span><span class="o">**</span><span class="mf">2.0</span> <span class="o">+</span> <span class="n">b</span><span class="o">**</span><span class="mf">2.0</span><span class="p">)</spa