compute diffs for each png files in the directory.

diffs.sh

#!/usr/bin/env zsh

if [ $# -ne 2 ]; then
    echo "$# args specified" 1>&2
    echo "usage: sh ./diffs.sh marker_filename target_directory" 1>&2
    exit 1
fi

for target in $2/*.png
do
    result=`compare -metric AE $1 $target - 2>&1 >/dev/null`
    echo $result $1 $target
done