#!/bin/bash
#
# Developed by Fred Weinhaus 12/30/2009 .......... revised 12/6/2023
#
# ------------------------------------------------------------------------------
# 
# Licensing:
# 
# Copyright © Fred Weinhaus
# 
# My scripts are available free of charge for non-commercial use, ONLY.
# 
# For use of my scripts in commercial (for-profit) environments or 
# non-free applications, please contact me (Fred Weinhaus) for 
# licensing arrangements. My email address is fmw at alink dot net.
# 
# If you: 1) redistribute, 2) incorporate any of these scripts into other 
# free applications or 3) reprogram them in another scripting language, 
# then you must contact me for permission, especially if the result might 
# be used in a commercial or for-profit environment.
# 
# My scripts are also subject, in a subordinate manner, to the ImageMagick 
# license, which can be found at: http://www.imagemagick.org/script/license.php
# 
# ------------------------------------------------------------------------------
# 
####
#
# USAGE: similar [-m mode] infile1 infile2
# USAGE: similar [-h or -help]
# 
# OPTIONS:
# 
# -m      mode       colorspace mode; g (for grayscale) or rgb; default=g
# 
###
# 
# NAME: SIMILAR 
# 
# PURPOSE: To compute the normalized cross correlation similarity metric 
# between two equal dimensioned images.
# 
# DESCRIPTION: SIMILAR computes the normalized cross correlation similarity 
# metric between two equal dimensioned images. The normalized cross correlation 
# metric measures how similar two images are, not how different they are. The  
# range of ncc metric values is between 0 (dissimilar) and 1 (similar). If
# mode=g, then the two images will be converted to grayscale. If mode=rgb, 
# then the two images first will be converted to colorspace=rgb. Next, the 
# ncc similarity metric will be computed for each channel. Finally, they will 
# be combined into an rms value. NOTE: this metric does not work for constant 
# color channels as it produces an ncc metric = 0/0 for that channel. Thus 
# it is not advised to run the script with either image having a totally 
# opaque or totally transparent alpha channel that is enabled.
# 
# 
# ARGUMENTS: 
# 
# -m mode ... MODE for colorspace to use when applying the normalized cross 
# correlation metric on the two images. If mode=g, then the two image will be 
# converted to grayscale. If mode=rgb, then the ncc similarity metric will be 
# computed for each channel and then combined as its rms value. Default=g
# 
# NOTE: For best accuracy, this script should be run in HDRI compilation of IM.
# 
# For reference on the normalized cross correlation metric, see 
# http://en.wikipedia.org/wiki/Cross-correlation#Normalized_cross-correlation
# 
# CAVEAT: No guarantee that this script will work on all platforms, 
# nor that trapping of inconsistent parameters is complete and 
# foolproof. Use At Your Own Risk. 
# 
######
# 

# set default values
mode="g"			# g or rgb

# set directory for temporary files
dir="."    # suggestions are dir="." or dir="/tmp"

# set up functions to report Usage and Usage with Description
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program
usage1() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^###/g;  /^#/!q;  s/^#//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}
usage2() 
	{
	echo >&2 ""
	echo >&2 "$PROGNAME:" "$@"
	sed >&2 -e '1,/^####/d;  /^######/g;  /^#/!q;  s/^#*//;  s/^ //;  4,$p' "$PROGDIR/$PROGNAME"
	}


# function to report error messages
errMsg()
	{
	echo ""
	echo $1
	echo ""
	usage1
	exit 1
	}


# function to test for minus at start of value of second part of option 1 or 2
checkMinus()
	{
	test=`echo "$1" | grep -c '^-.*$'`   # returns 1 if match; 0 otherwise
    [ $test -eq 1 ] && errMsg "$errorMsg"
	}

# test for correct number of arguments and get values
if [ $# -eq 0 ]
	then
	# help information
   echo ""
   usage2
   exit 0
elif [ $# -gt 4 ]
	then
	errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---"
else
	while [ $# -gt 0 ]
		do
			# get parameter values
			case "$1" in
		  -h|-help)    # help information
					   echo ""
					   usage2
					   exit 0
					   ;;
				-m)    # get mode
					   shift  # to get the next parameter
					   # test if parameter starts with minus sign 
					   errorMsg="--- INVALID MODE SPECIFICATION ---"
					   checkMinus "$1"
					   mode="$1"
					   mode=`echo "$mode" | tr "[:upper:]" "[:lower:]"`
					   case "$mode" in 
					   		gray|grayscale|g) mode="g" ;;
					   		rgb) mode="rgb" ;;
					   		*) errMsg "--- MODE=$mode IS AN INVALID VALUE ---" 
					   	esac
					   ;;
				 -)    # STDIN and end of arguments
					   break
					   ;;
				-*)    # any other - argument
					   errMsg "--- UNKNOWN OPTION ---"
					   ;;
		     	 *)    # end of arguments
					   break
					   ;;
			esac
			shift   # next option
	done
	#
	# get infile and outfile
	infile1="$1"
	infile2="$2"
	[ "$3" != "" ] && errMsg "--- TOO MANY IMAGES SPECIFIED ---"
fi

# test that infile1 provided
[ "$infile1" = "" ] && errMsg "--- NO INPUT FILE 1 SPECIFIED ---"

# test that outfile provided
[ "$infile2" = "" ] && errMsg "--- NO INPUT FILE 2 SPECIFIED ---"

# test if both files have alpha channel enabled
# get channels as gray, graya, rgb, rgba, cmyk, cmyka, etc
channels1=`convert $infile1 -ping -format "%[channels]" info:`
channels2=`convert $infile2 -ping -format "%[channels]" info:`
# split channels into array of characters
charArr1=(`echo $channels1 | fold -w 1`)
charArr2=(`echo $channels2 | fold -w 1`)
# test if last character is "a"
num1=${#charArr1[*]}
num2=${#charArr2[*]}
lastchar1="${charArr1[$num1-1]}"
lastchar2="${charArr2[$num2-1]}"
if [ "$lastchar1" = "a" -a "$lastchar2" = "a" ]; then
	aon="yes"
elif [ "$lastchar1" != "a" -a "$lastchar2" != "a" ]; then
	aon="no"
else
	errMsg "--- ALPHA CHANNEL MUST BE ON IN BOTH IMAGES OR OFF IN BOTH IMAGES ---" 
fi

# set up temp file
tmpA1="$dir/similar_1_$$.mpc"
tmpB1="$dir/similar_1_$$.cache"
tmpA2="$dir/similar_2_$$.mpc"
tmpB2="$dir/similar_2_$$.cache"
tmpA3="$dir/similar_3_$$.mpc"
tmpB3="$dir/similar_3_$$.cache"
tmpA4="$dir/similar_4_$$.mpc"
tmpB4="$dir/similar_4_$$.cache"

trap "rm -f $tmpA1 $tmpB1 $tmpA2 $tmpB2 $tmpA3 $tmpB3 $tmpA4 $tmpB4;" 0
trap "rm -f $tmpA1 $tmpB1 $tmpA2 $tmpB2 $tmpA3 $tmpB3 $tmpA4 $tmpB4; exit 1" 1 2 3 15
#trap "rm -f $tmpA1 $tmpB1 $tmpA2 $tmpB2 $tmpA3 $tmpB3 $tmpA4 $tmpB4; exit 1" ERR

# get im_version
im_version=`convert -list configure | \
	sed '/^LIB_VERSION_NUMBER */!d; s//,/;  s/,/,0/g;  s/,0*\([0-9][0-9]\)/\1/g' | head -n 1`

# colorspace RGB and sRGB swapped between 6.7.5.5 and 6.7.6.7 
# though probably not resolved until the latter
# then -colorspace gray changed to linear between 6.7.6.7 and 6.7.8.2 
# then -separate converted to linear gray channels between 6.7.6.7 and 6.7.8.2,
# though probably not resolved until the latter
# so -colorspace HSL/HSB -separate and -colorspace gray became linear
# but we need to use -set colorspace RGB before using them at appropriate times
# so that results stay as in original script
# The following was determined from various version tests using similar.
# with IM 6.6.0.10, 6.6.1.10, 6.6.2.10, 6.7.4.10, 6.7.6.10, 6.7.9.0
# Note: prior to about 6.6.1.10 and certainly for 6.6.0.10 values are different
if [ "$im_version" -lt "06070607" -o "$im_version" -gt "06070707" ]; then
	setcspace="-set colorspace RGB"
else
	setcspace=""
fi
if [ "$im_version" -ge "06070606" ]; then
	cspace="sRGB"
else
	cspace="RGB"
fi
# no need for setcspace for grayscale or channels after 6.8.5.4
if [ "$im_version" -gt "06080504" ]; then
	setcspace=""
	cspace="sRGB"
fi


# set up colorspace conversion
if [ "$mode" = "g" ]; then
	cspace="$setcspace -colorspace gray"
else
	cspace="-colorspace $cspace"
fi

# read the input images into the temp files and test validity.
convert -quiet "$infile1" $cspace +repage "$tmpA1" ||
	errMsg "--- FILE $infile1 DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAS ZERO SIZE  ---"
convert -quiet "$infile2" $cspace +repage "$tmpA2" ||
	errMsg "--- FILE $infile2 DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAS ZERO SIZE  ---"

# test image sizes
w1=`convert $tmpA1 -ping -format "%w" info:`
w2=`convert $tmpA2 -ping -format "%w" info:`
h1=`convert $tmpA1 -ping -format "%h" info:`
h2=`convert $tmpA2 -ping -format "%h" info:`
if [ $w1 -ne $w2 -a $h1 -ne $h2 ]; then 
	errMsg "--- IMAGES MUST BE THE SAME WIDTH AND HEIGHT ---"
fi

#function to compute single channel NCC metric
nccMetric()
	{
	img1=$1
	img2=$2
	m1=`convert $img1 -format "%[fx:mean]" info:`
	m2=`convert $img2 -format "%[fx:mean]" info:`
	m12=`convert xc: -format "%[fx:$m1*$m2]" info:`
	s1=`convert $img1 -format "%[fx:standard_deviation]" info:`
	s2=`convert $img2 -format "%[fx:standard_deviation]" info:`
	#echo "m1=$m1; m2=$m2; s1=$s1; s2=$s2"
	if [ "$s1" = "0" -o "$s2" = "0" ]; then
		errMsg "--- ONE OR BOTH IMAGES ARE CONSTANT VALUES (NCC=0/0) ---"
	else
		# -compose mathematics ... is equivalent to -fx "(u-$m1)*(v-$m2)"
		ncc=`convert $img1 $img2 -set option:compose:args "1,-$m1,-$m2,$m12" \
			-compose mathematics -composite -format "%[fx:mean/($s1*$s2)]" info:`
	fi
	}


if [ "$mode" = "g" ]; then
#	convert $tmpA1 $setcspace -channel g -separate $tmpA3
#	convert $tmpA2 $setcspace -channel g -separate $tmpA4
	nccMetric "$tmpA1" "$tmpA2"
	nccgray=$ncc
	if [ "$aon" = "yes" ]; then
		convert $tmpA1 -alpha extract $tmpA3
		convert $tmpA2 -alpha extract $tmpA4
		nccMetric "$tmpA3" "$tmpA4"
		nccalpha=$ncc
		ncc=`convert xc: -format \
			"%[fx:sqrt(($nccgray^2 + $nccalpha^2)/2)]" info:`
	else
		ncc=$nccgray
	fi
	echo "Similarity Metric: $ncc"
else
	convert $tmpA1 $setcspace -channel red -separate $tmpA3
	convert $tmpA2 $setcspace -channel red -separate $tmpA4
	nccMetric "$tmpA3" "$tmpA4"
	nccred=$ncc

	convert $tmpA1 $setcspace -channel green -separate $tmpA3
	convert $tmpA2 $setcspace -channel green -separate $tmpA4
	nccMetric "$tmpA3" "$tmpA4"
	nccgreen=$ncc

	convert $tmpA1 $setcspace -channel blue -separate $tmpA3
	convert $tmpA2 $setcspace -channel blue -separate $tmpA4
	nccMetric "$tmpA3" "$tmpA4"
	nccblue=$ncc
	
	if [ "$aon" = "yes" ]; then
	convert $tmpA1 -alpha extract $tmpA3
	convert $tmpA2 -alpha extract $tmpA4
	nccMetric "$tmpA3" "$tmpA4"
	nccalpha=$ncc
	ncc=`convert xc: -format \
		"%[fx:sqrt(($nccred^2 + $nccgreen^2 + $nccblue^2 + $nccalpha^2)/4)]" info:`
	else
	ncc=`convert xc: -format \
		"%[fx:sqrt(($nccred^2 + $nccgreen^2 + $nccblue^2)/3)]" info:`
	fi
	echo "Similarity Metric: $ncc"
	echo "red=$nccred; green=$nccgreen; blue=$nccblue;"
fi
echo ""