add caption to picture...

caption.sh

#!/bin/bash

[[ "$#" -eq 2 ]] || { echo "Usage: ${0} pict.ure \"caption text\"" >&2; exit 1; }

convert \
-size $(identify -format %w ${1})x40 \
-background transparent \
-gravity center \
-font Helvetica-Bold \
-fill yellow \
-pointsize 40 \
caption:"${2}" ${1} \
+swap \
-gravity south \
-composite ${1%.*}_${2}.png