#!/usr/bin/env bash
# usage: diff-pair.sh <before.png> <after.png> <outprefix> [fuzz%]
# Writes <outprefix>-diff0.png (fuzz 0, every changed pixel painted red, amplified) and
# <outprefix>-diffT.png (fuzz N%, default 10). Prints changed-pixel counts.
b=$1 a=$2 o=$3 f=${4:-10}
n0=$(compare -metric AE -fuzz 0 -highlight-color red -lowlight-color '#202020' "$b" "$a" "$o-diff0.png" 2>&1)
nT=$(compare -metric AE -fuzz "$f%" -highlight-color red -lowlight-color '#202020' "$b" "$a" "$o-diffT.png" 2>&1)
echo "$(basename "$o") AE0=$n0 AE@${f}%=$nT"