show_usage () {
	echo "-c         crop image from center"
	echo "-n         fit full image to screen"
}
...
OPT_CENTER=""
OPT_NOCROP=""
...
while getopts :h,:c,:n,:l,f:,u: option
do
	case "$option" in
		c) OPT_CENTER="true" ;;
		n) OPT_NOCROP="true" ;;
	esac
done
...
[[ -n $OPT_CENTER ]] && [[ -n $OPT_NOCROP ]] && echo "$SCRIPTNAME: must specify either -c or -n" && exit 1 ;
...
set --
[ -n "$OPT_CENTER" ] && set -- "$@" --ez center "$OPT_CENTER"
[ -n "$OPT_NOCROP" ] && set -- "$@" --ez nocrop "$OPT_NOCROP"
/data/data/com.termux/files/usr/libexec/termux-api Wallpaper "$@"