compare two folders with images visually and output mean squared error for each pair

compare.sh

#!/bin/bash

# Usage:
# ./compare.sh folder1 folder2 | grep -v '^[0-9]\.[0-9]\+e-' | grep -v '^0 ' | sort --numeric-sort --reverse
# filters out images with significant differences and sorts them by mean squared error

cd "$1"
for file in $(find * -type f); do
    # http://www.imagemagick.org/Usage/compare/
    NORMALIZED_DIFFERENCE=$(compare -metric MSE "$file" ../"$2"/"$file" null: 2>&1 | cut -d '(' -f 2 | cut -d ')' -f 1)
    echo "$NORMALIZED_DIFFERENCE" "$file"
done