      | &#39;Q,aS,bS&#39; or str, optional</span>
<span class="sd">            | &#39;Q,aS,bS&#39; (brightness and opponent signals for saturation)</span>
<span class="sd">            |  other options: &#39;Q,aM,bM&#39; (colorfulness) </span>
<span class="sd">            |                 (Note that &#39;Q,aW,bW&#39; would lead to a Cartesian </span>
<span class="sd">            |                  a,b-coordinate system centered at (1,0))</span>
<span class="sd">            | Str specifying the type of </spa