simple watermark script

#!/bin/bash
# from http://www.imagemagick.org/Usage/annotating/
# requires ImageMagick!
if [ "$2" ]; then marked_up="$2"
else marked_up="$(dirname "$1")/watermarked_$(basename "$1")"
fi
if [ "$3" ]; then markup=$3; else markup="author@photography.com"; fi
if [ "$4" ]; then location=$4; else location=southwest; fi
convert -size 200x14 xc:none -gravity center \
 -stroke black -strokewidth 2 -annotate 0 "$markup" \
 -background none -shadow 100x3+0+0 +repage \
 -stroke none -fill white     -annotate 0 "$markup" \
 "$1"  +swap -gravity $location -geometry +0-3 \
 -composite $marked_up