screen brightness auto ajustment according to lighting

#!/bin/bash
TMPFILE=`mktemp /tmp/tmp.XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX.jpg`
fswebcam --jpeg 95 $TMPFILE
AVG=`convert $TMPFILE -format "%[mean]" info:`
BRIGHT=`echo $AVG | awk '{print int($1/65535*100+30)}'`
xbacklight -set $BRIGHT -time 2000
rm -rf $TMPFILE