#!/bin/bash
#
# Developed by Fred Weinhaus 5/17/2011 .......... revised 4/25/2015
#
# ------------------------------------------------------------------------------
# 
# 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: entropy infile
# USAGE: entropy [-h or -help]
# 
# OPTIONS:
# 
# -h or -help     Displays help information
# 
###
# 
# NAME: ENTROPY 
# 
# PURPOSE: To compute the normalized entropy of an image channel-by-channel.
# 
# DESCRIPTION: ENTROPY computes the normalized entropy of an image 
# channel-by-channel. Entropy is a measure of graylevel distribution 
# (disorder or randomness) in the histogram. It is not a measure of spatial 
# disorder or spatial randomness in the image. The entropy is computed from 
# the histogram of the channel by accumulating -p*ln(p) over every 8-bit 
# graylevel, where p = (count for a given graylevel) / (total pixels). 
# The normalized entropy is equal to the entropy/ln(256). For example, if the 
# image is a single grayscale, then the entropy=0. If the image is a uniform 
# gradient including all values from 0 to 255 that are equally populated in 
# the histogram, then the entropy=1.
#
# When the colorspace is Gray, only one Gray entropy value will be printed. 
#
# When the colorspace is CMYK, the following 5 values will be printed: 
# Cyan, Magenta, Yellow and Black Entropies and the Average of those four 
# entropies.
# 
# When the colorspace is RGB or any other colorspace, then the following 4 
# values will be printed to the terminal:  Red, Green and Blue Entropies and 
# the Average of those three entropies. For any colorspace other than RGB, 
# then Red, Green and Blue should then be interpreted as channels 1, 2 and 3, 
# respectively, for that colorspace.
# 
# NOTE: This script will process only the first frame/page of a multiframe or 
# multipage image.
#
# 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

# 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 1 ]
	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
					   ;;
				 -)    # STDIN and end of arguments
					   break
					   ;;
				-*)    # any other - argument
					   errMsg "--- UNKNOWN OPTION ---"
					   ;;
		     	 *)    # end of arguments
					   break
					   ;;
			esac
			shift   # next option
	done
	#
	# get infile
	infile="$1"
fi

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


# setup temporary images and auto delete upon exit
tmpA1="$dir/entropy_1_$$.mpc"
tmpB1="$dir/entropy_1_$$.cache"
trap "rm -f $tmpA1 $tmpB1;" 0
trap "rm -f $tmpA1 $tmpB1; exit 1" 1 2 3 15
trap "rm -f $tmpA1 $tmpB1; exit 1" ERR

# read the input image and filter image into the temp files and test validity.
convert -quiet "$infile[0]" +repage "$tmpA1" ||
	errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAS ZERO SIZE  ---"

# get total number of pixels
totpix=`convert $tmpA1 -ping -format "%[fx:w*h]" info:`
#echo "totpix=$totpix"

# get colorspace
cspace=`convert $tmpA1 -format "%[colorspace]" info:`
#echo "cspace=$cspace"

echo ""
if [ "$cspace" = "Gray" -o "$cspace" = "Rec709Luma" -o "$cspace" = "Rec601Luma" ]; then

	# get gray entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	gray_entropy=$(convert $tmpA1 -channel r -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; gray_entropy += -p*log(p); numbins++; }
	END { print gray_entropy/log(numbins); } ')
	echo "Gray Entropy = $gray_entropy"


elif [ "$cspace" = "CMYK" ]; then

	# get cyan entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	cyan_entropy=$(convert $tmpA1 -channel c -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; cyan_entropy += -p*log(p); numbins++; }
	END { print cyan_entropy/log(numbins); } ')

	# get magenta entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	magenta_entropy=$(convert $tmpA1 -channel m -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; magenta_entropy += -p*log(p); numbins++; }
	END { print magenta_entropy/log(numbins); } ')

	# get yellow entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	yellow_entropy=$(convert $tmpA1 -channel y -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; yellow_entropy += -p*log(p); numbins++; }
	END { print yellow_entropy/log(numbins); } ')

	# get black entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	black_entropy=$(convert $tmpA1 -channel k -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; black_entropy += -p*log(p); numbins++; }
	END { print black_entropy/log(numbins); } ')

	ave_entropy=`echo "scale=6; ($cyan_entropy+$magenta_entropy+$yellow_entropy+$black_entropy)/4" | bc`

	echo "Cyan Entropy = $cyan_entropy"
	echo "Magenta Entropy = $magenta_entropy"
	echo "Yellow Entropy = $yellow_entropy"
	echo "Black Entropy = $black_entropy"
	echo "Average CMYK Entropy = $ave_entropy"

else

	# get red entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	red_entropy=$(convert $tmpA1 -channel r -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; red_entropy += -p*log(p); numbins++; }
	END { print red_entropy/log(numbins); } ')

	# get green entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	green_entropy=$(convert $tmpA1 -channel g -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; green_entropy += -p*log(p); numbins++; }
	END { print green_entropy/log(numbins); } ')

	# get blue entropy from red channel
	# get histogram, remove all chars not numeric or space and collapse multiple spaces
	# use NF>1 (i.e. number of fields > 1) in AWK to remove empty lines or lines with only one field 
	blue_entropy=$(convert $tmpA1 -channel b -separate -depth 8 -format "%c" -define histogram:unique-colors=true histogram:info:- |\
	tr -cs '0-9\012' ' ' |\
	awk -v totpix="$totpix" ' 
	NF>1 { p = $1/totpix; blue_entropy += -p*log(p); numbins++; }
	END { print blue_entropy/log(numbins); } ')

	ave_entropy=`echo "scale=6; ($red_entropy+$green_entropy+$blue_entropy)/3" | bc`

	echo "Red Entropy = $red_entropy"
	echo "Green Entropy = $green_entropy"
	echo "Blue Entropy = $blue_entropy"
	echo "Average RGB Entropy = $ave_entropy"

fi
echo ""
exit 0