prep_degree_default=90
prep() {
    if [ $# -eq 2 ]; then
        prep_degree_default=$1		# degrees optional first arg
	shift
    fi
    image=$1				# image name is second or only arg
    degrees=$prep_degree_default
    if [ $degrees -ne 0 ]; then
	rotate $degrees $image
    fi
    xv $image
}

rotate() {
    degrees=$1
    image=$2
    convert -rotate $degrees $image $image~
    mv -f $image~ $image
}