#!/bin/bash
# 
# Developed by Fred Weinhaus 5/14/2009 .......... revised 9/5/2019
#
# ------------------------------------------------------------------------------
# 
# 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: trimmer [-s sides] [-f fuzzval] [-b bcolor] [-g gcolor] infile outfile
# USAGE: trimmer [-h or -help]
# 
# OPTIONS:
# 
# -s       sides        comma delimited list of sides to trim; list can include 
#                       any combination of: north, east, south, west or just "all"; 
#                       default=north
# -f       fuzzamt      fuzz amount in percent for trimming border color; float; 
#                       fuzzamt>=0; default=0
# -b       bcolor       background color for area to trim; any valid IM color 
#                       may be specified; default will be determined automatically 
#                       from the average color of all specified sides
# -g       gcolor       guard color used to preserve sides not be trimmed; 
#                       any valid IM color that is further from the background color 
#                       than the fuzzval; default will be determined automatically 
#                       as either the complement of the background color, black or 
#                       white whichever is furthest from the background color.
# 
###
# 
# NAME: TRIMMER 
#  
# PURPOSE: To trim the background from any number of specified sides of an image.
# 
# DESCRIPTION: TRIMMER trims the background from any number of specified sides 
# of an image. The user may specify from one to four sides as a comma delimited list 
# that is enclosed in quotes. A fuzz value may be specified if the background is not 
# a constant color.
# 
# 
# Arguments: 
# 
# -s sides --- SIDES is a comma delimited list of the sides to be trimmed enclosed 
# in quotes. Any number of sides from one to four may be specified. The list can 
# include any combination of: north, east, south, west or just "all". 
# The default=north.
# 
# -f fuzzamt --- FUZZAMT is the fuzz amount specified as a float percent greater 
# than zero (without the % sign). The default is zero which indicates that border 
# is a uniform color. Larger values are needed when the border is not a uniform color.
# 
# -b bcolor --- BCOLOR is the background color for the area to trim. Any valid IM  
# color may be specified. The default will be determined automatically from the  
# average color of all specified sides. There is no guarantee that this will be 
# accurate. So if it does not work, then you will need to supply the border color.
# 
# -g gcolor --- GCOLOR is the guard color used to preserve the side that are not 
# to be trimmed. Any valid IM color may be specified that is further from the 
# background color than the fuzzval. The default will be determined automatically 
# as either the complement of the background color, black or white whichever is 
# furthest from the background color. There is no guarantee that this will be 
# accurate. So if it does not work, then you will need to supply the guard color.
# 
# NOTE: This script will not trim more than half way in any dimension. Also for 
# images with transparency, you will have to provide a guard color.
# 
# 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; 
sides="north"			# comma delimited list: north, south, east, west, all
fuzzamt=0				# fuzz amount in percent
bcolor=""				# background color; use none for transparent background
gcolor=""				# guard color

# 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 10 ]
	then
	errMsg "--- TOO MANY ARGUMENTS WERE PROVIDED ---"
else
	while [ $# -gt 0 ]
		do
		# get parameters
		case "$1" in
	  -h|-help)    # help information
				   echo ""
				   usage2
				   ;;
			-s)    # sides
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID SIDES SPECIFICATION ---"
				   checkMinus "$1"
				   sides=$1
				   # further testing done later
				   ;;
			-f)    # fuzzamt
				   shift  # to get the next parameter - fuzzval
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID FUZZAMT SPECIFICATION ---"
				   checkMinus "$1"
				   fuzzamt=`expr "$1" : '\([.0-9]*\)'`
				   [ "$fuzzamt" = "" ] && errMsg "--- FUZZAMT=$fuzzamt MUST BE A NON-NEGATIVE FLOATING POINT VALUE (with no sign) ---"
				   fuzzamttest=`echo "$fuzzamt < 0" | bc`
				   [ $fuzzamttest -eq 1 ] && errMsg "--- FUZZAMT=$fuzzamt MUST BE A NON-NEGATIVE FLOATING POINT VALUE ---"
				   ;;
			-b)    # bcolor
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID BACKGROUND COLOR SPECIFICATION ---"
				   checkMinus "$1"
				   bcolor=$1
				   ;;
			-g)    # gcolor
				   shift  # to get the next parameter
				   # test if parameter starts with minus sign 
				   errorMsg="--- INVALID GUARD COLOR SPECIFICATION ---"
				   checkMinus "$1"
				   gcolor=$1
				   ;;
			 -)    # 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
	infile="$1"
	outfile="$2"
fi

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

# test that outfile provided
[ "$outfile" = "" ] && errMsg "NO OUTPUT FILE SPECIFIED"

# setup temporary files
tmpA="$dir/trimmer_$$.mpc"
tmpB="$dir/trimmer_$$.cache"
trap "rm -f $tmpA $tmpB;" 0
trap "rm -f $tmpA $tmpB; exit 1" 1 2 3 15
trap "rm -f $tmpA $tmpB; exit 1" ERR

# read the input image into the TMP cached image.
convert -quiet "$infile" +repage "$tmpA" ||
	errMsg "--- FILE $infile NOT READABLE OR HAS ZERO SIZE ---"


# get sides as array
sides=`echo "$sides" | tr "[:upper:]" "[:lower:]"`
# add comma to end, then remove spaces, then change commas to spaces
sides_list=`echo "${sides}," | sed -n 's/[ ]*//gp' | tr "," " "`
sidesArray=($sides_list)
num=${#sidesArray[*]}


# test valid sides
i=0
while [ $i -lt $num ]; do
	side="${sidesArray[$i]}"
	case "$side" in 
		north) ;;
		east) ;;
		south) ;;
		west) ;;
		all) ;;
		*) echo "--- INVALID SIDE SPECIFIED ---" ;;
	esac
	i=`expr $i + 1`
done


# strip duplicate sides
# change space delimited list to list of one-word rows
# note \012 is octal for line break
sides_list=`echo "$sides_list" | tr " " "\012"`

# sort list of rows to reorder and remove duplicates
sides_list=`echo $sides_list | sort -u`

# use grep '.*' to put back into space delimited list from sorted rows
sides_list=`echo $sides_list | grep '.*'`


# process image if sides=all or all 4 sides provided, then exit 0
# otherwise continute
if [ "$sides_list" = "all" -o $num -eq 4 ]; then
	convert $tmpA -fuzz ${fuzzamt}% -trim +repage $outfile
	exit 0
fi


# change sides to "remove" to sides to "preserve" by 
# deleting elements from list of all possible values
pSidesArray=(north east south west)
i=0
while [ $i -lt $num ]; do
	side="${sidesArray[$i]}"
	[ "$side" = "north" ] && pnum=0
	[ "$side" = "east" ] && pnum=1
	[ "$side" = "south" ] && pnum=2
	[ "$side" = "west" ] && pnum=3
	unset pSidesArray[$pnum]
	i=`expr $i + 1`
done
pnum="${#pSidesArray[*]}"

# NOTE: must reset array from list to remove empty and non-showing elements
# produced by unset, so that the new array can be indexed properly again.
pSidesArray=(${pSidesArray[*]})
pnum="${#pSidesArray[*]}"


if [ "$bcolor" = "" ]; then
	# get average color of specified sides
	
	# get width and height and sides to be removed
	ww=`identify -ping -format "%w" $tmpA`
	hh=`identify -ping -format "%h" $tmpA`
	[ "${sidesArray[0]}" != "" ] && side1="${sidesArray[0]}"
	[ "${sidesArray[1]}" != "" ] && side2="${sidesArray[1]}"
	[ "${sidesArray[2]}" != "" ] && side3="${sidesArray[2]}"
	[ "${sidesArray[3]}" != "" ] && side4="${sidesArray[3]}"
	
	# get average colors for all four outer edges
	color_north=`convert ${infile} -gravity north -crop ${ww}x1+0+0 +repage -format '%[pixel:s.p{0,0}]' info:`
	color_east=`convert ${infile} -gravity east -crop 1x${hh}+0+0 +repage -format '%[pixel:s.p{0,0}]' info:`
	color_south=`convert ${infile} -gravity south -crop ${ww}x1+0+0 +repage -format '%[pixel:s.p{0,0}]' info:`
	color_west=`convert ${infile} -gravity west -crop 1x${hh}+0+0 +repage -format '%[pixel:s.p{0,0}]' info:`

	# compute global average from only edges (averages) to be removed
	# use that for background color
	if [ $num -eq 1 ]; then
		eval color1="\${color_${side1}}"
		bcolor="$color1"
	elif [ $num -eq 2 ]; then
		eval color1="\${color_${side1}}"
		eval color2="\${color_${side2}}"
		bcolor=`convert xc: -format "%[pixel:($color1+$color2)/2]" info:`
	elif [ $num -eq 3 ]; then
		eval color1="\${color_${side1}}"
		eval color2="\${color_${side2}}"
		eval color3="\${color_${side3}}"
		bcolor=`convert xc: -format "%[pixel:($color1+$color2+$color3)/3]" info:`
	elif [ $num -eq 4 ]; then
		eval color1="\${color_${side1}}"
		eval color2="\${color_${side2}}"
		eval color3="\${color_${side3}}"
		eval color4="\${color_${side4}}"
		bcolor=`convert xc: -format "%[pixel:($color1+$color2+$color3+$color4)/4]" info:`
	fi
fi


if [ "$gcolor" = "" ]; then
	# get color complement (negate) to background color for possible guard color

	# note: negating the alpha channel does not work for opaque white "rgba(255,255,255,1)"
	# as ncolor becomes "none" as does not make a good guard color
	# so just negate ignoring the alpha channel
	# that seems to work
	ncolor=`convert -size 1x1 xc:"$bcolor" \
		-negate -format '%[pixel:s.p{0,0}]' info:`
	
	# test differnce between background color (in percent) with complement (in percent) 
	# and also with opaque black and opaque white
	# choose color that is furtherest (largest diff) from background color 
	# to use as guard color
	diffn=`compare -metric rmse -size 1x1 xc:"$bcolor" xc:"$ncolor" null: 2>&1 | \
		sed -n 's/^.*[(]\(.*\)[)].*$/\1/p'`
	diffb=`compare -metric rmse -size 1x1 xc:"$bcolor" xc:"black" null: 2>&1 | \
		sed -n 's/^.*[(]\(.*\)[)].*$/\1/p'`
	diffw=`compare -metric rmse -size 1x1 xc:"$bcolor" xc:"white" null: 2>&1 | \
		sed -n 's/^.*[(]\(.*\)[)].*$/\1/p'`
	diff_max=`convert xc: -format "%[fx:max(max($diffn,$diffb),$diffw)]" info:`
	if [ "$diffn" = "$diff_max" ]; then
		gcolor="$ncolor"
	elif [ "$diffb" = "$diff_max" ]; then
		gcolor="black"
	elif [ "$diffw" = "$diff_max" ]; then
		gcolor="white"
	fi
fi


# set up spice and chop amounts
i=0
while [ $i -lt $pnum ]; do
	side=${pSidesArray[$i]}
	if [ "$side" = "north" ]; then
		amountsArray[$i]="0x1+0+0"
	elif [ "$side" = "south" ]; then
		amountsArray[$i]="0x1+0+0"
	elif [ "$side" = "west" ]; then 
		amountsArray[$i]="1x0+0+0"
	elif [ "$side" = "east" ]; then
		amountsArray[$i]="1x0+0+0"
	fi
	i=`expr $i + 1`
done


# set up command sequences
# splice
splicer=""
i=0
while [ $i -lt $pnum ]; do
	splicer="$splicer -gravity ${pSidesArray[$i]} -splice ${amountsArray[$i]}"
	i=`expr $i + 1`
done


# composite
composer=""
i=0
while [ $i -lt $pnum ]; do
	composer="$composer -size 1x1 xc:$gcolor -gravity ${pSidesArray[$i]} -composite"
	i=`expr $i + 1`
done


# chop
chopper=""
i=0
while [ $i -lt $pnum ]; do
	chopper="$chopper -gravity ${pSidesArray[$i]} -chop ${amountsArray[$i]}"
	i=`expr $i + 1`
done


# do trimming
convert $tmpA \
	-background "$bcolor" $splicer \
	$composer \
	-fuzz ${fuzzamt}% -trim +repage \
	$chopper \
	"$outfile"

exit 0