b></a>,
<a href="http://www.lispworks.com/documentation/HyperSpec/Body/t_t.htm"><b>t</b></a>

<p><b>Description:</b> <p>An image is a three-dimensional array of
<tt>(unsigned-byte 8)</tt> or <tt>(unsigned-byte 16)</tt>.  The three
dimensions represent row, column, and <a
href="http://en.wikipedia.org/wiki/Channel_(digital_image)">channel</a>.
In other words, <tt>(aref image i j k)</tt> is the intensity in the
<tt>k</tt>-th channel of the pixel in the <tt>i</tt>-th row and
<tt>j</tt>-th column of <tt>image</