 '.r')</span>
0146 <span class="comment">% %</span>
0147 <span class="comment">%</span>
0148         <span class="comment">%grab whatever the background was before the fly got there.</span>
0149         temp = background(sqr(1):sqr(2),sqr(3):sqr(4));
0150         <span class="comment">%update</span>
0151         background = alpha*background+(1-alpha)*img;
0152         <span class="comment">%make sure we only update image outside of fly</span>
0153         background(sqr(1):sqr(2),sqr(3):sqr(4)) = temp;
015