nd &#39;ab&#39; options </span>
<span class="sd">            |              and returns them as a tuple.</span>
<span class="sd">        :KLCH: </span>
<span class="sd">            | None, optional</span>
<span class="sd">            | Weigths for L, C, H </span>
<span class="sd">            | None: default to [1,1,1] </span>
<span class="sd">        :avg:</span>
<span class="sd">            | None, optional</span>
<span class="sd">            | None: don&#39;t calculate average DE, </span>
<span class="sd"