n class="keyword">namespace </span>boost { <span class="keyword">namespace </span>gil {
<a name="l00038"></a>00038 
<a name="l00039"></a>00039 <span class="comment">// Forward-declare gray_t</span>
<a name="l00040"></a>00040 <span class="keyword">struct </span>gray_color_t;
<a name="l00041"></a>00041 <span class="keyword">typedef</span> mpl::vector1&lt;gray_color_t&gt; gray_t;
<a name="l00042"></a>00042 <span class="keyword">template</span> &lt;<span class="keyword">typename</span> PixelBased&gt; <span clas