al">&gt;&amp;</span> <span class="identifier">strm</span><span class="special">,</span> <span class="identifier">rectangle</span><span class="special">&amp;</span> <span class="identifier">r</span><span class="special">);</span>
</pre>
<p>
        </p>
<p>
          As it was said, the rectangle is described by two points - the top left
          and the bottom right corners of the rectangle area. Now let's extend our
          filter factory with the <code class="computeroutput"><span class="identifier">on