Bash script that duplicates the functionality of VirtualGL's imgdiff program using ImageMagick, in a more compatible (and probably more accurate) way

imdiff

#!/bin/bash

# Copyright (C)2019 D. R. Commander.  All Rights Reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
# - Redistributions of source code must retain the above copyright notice,
#   this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright notice,
#   this list of conditions and the following disclaimer in the documentation
#   and/or other materials provided with the distribution.
# - Neither the name of The VirtualGL Project nor the names of its contributors
#   may be used to endorse or promote products derived from this software
#   without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS",
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

set -e
set -u

if [ $# -lt 2 ]; then
	echo USAGE: $0 \<Image 1\> \<Image 2\>
	exit 1
fi

PAE=(`compare -verbose -metric PAE "$1" "$2" null: 2>&1 | grep -E 'red:|green:|blue:|all:' | cut -f2 -d: | sed s/\(.*//g`)
for index in {0..3}; do
	PAE[$index]=`echo ${PAE[$index]} | awk '{printf "%.0f", $1/256}'`
done

MAE=(`compare -verbose -metric MAE "$1" "$2" null: 2>&1 | grep -E 'red:|green:|blue:|all:' | cut -f2 -d: | sed s/\(.*//g`)
for index in {0..3}; do
	MAE[$index]=`echo ${MAE[$index]} | awk '{printf "%.6f", $1/256}'`
done

RMS=(`compare -verbose -metric RMSE "$1" "$2" null: 2>&1 | grep -E 'red:|green:|blue:|all:' | cut -f2 -d: | sed s/\(.*//g`)
for index in {0..3}; do
	RMS[$index]=`echo ${RMS[$index]} | awk '{printf "%.6f", $1/256}'`
done

PSNR=(`compare -verbose -metric PSNR "$1" "$2" null: 2>&1 | grep -E 'red:|green:|blue:|all:' | cut -f2 -d: | sed s/\(.*//g`)

echo B: max err.= ${PAE[2]} avg err.= ${MAE[2]} rms= ${RMS[2]} PSNR= ${PSNR[2]}
echo G: max err.= ${PAE[1]} avg err.= ${MAE[1]} rms= ${RMS[1]} PSNR= ${PSNR[1]}
echo R: max err.= ${PAE[0]} avg err.= ${MAE[0]} rms= ${RMS[0]} PSNR= ${PSNR[0]}
echo T: max err.= ${PAE[3]} avg err.= ${MAE[3]} rms= ${RMS[3]} PSNR= ${PSNR[3]}