#!/bin/bash
#
# Developed by Fred Weinhaus 10/29/2008 .......... revised 11/3/2015
#
# ------------------------------------------------------------------------------
# 
# 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: 2colorthresh infile outfile
# USAGE: 2colorthresh [-help]
#
# OPTIONS:
#
# There are no options
#
###
#
# NAME: 2COLORTHRESH
# 
# PURPOSE: To automatically thresholds an image to binary (b/w) format 
# using an adaptive spatial subdivision color reduction technique.
# 
# DESCRIPTION: 2COLORTHRESH automatically thresholds an image to binary 
# (b/w) format using an adaptive spatial subdivision color reduction 
# technique. This is the -colors IM operator as implemented with slight 
# modification from Anthony's Examples at 
# http://www.imagemagick.org/Usage/quantize/#two_color 
# For algorithm details, see http://www.imagemagick.org/script/quantize.php
# 
# OPTIONS: 
# 
# There are no options. 
# 
# NOTE: It is highly recommended that the output not be specified 
# as a JPG image as that will cause compression and potentially a 
# non-binary (i.e. a graylevel) result. GIF is the recommended 
# output format.
# 
# 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 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 2 ]
	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 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"


tmpA1="$dir/2colorsthresh_1_$$.mpc"
tmpA2="$dir/2colorsthresh_1_$$.cache"
trap "rm -f $tmpA1 $tmpA2; exit 0" 0
trap "rm -f $tmpA1 $tmpA2; exit 1" 1 2 3 15

if convert -quiet "$infile" +repage "$tmpA1"
	then
	: ' do nothing '
else
	errMsg "--- FILE $infile DOES NOT EXIST OR IS NOT AN ORDINARY FILE, NOT READABLE OR HAG ZERO SIZE ---"
fi	

# process image
convert $tmpA1 +dither -colors 2 -colorspace gray -contrast-stretch 0 "$outfile"

exit 0