#!/bin/bash
#
# Usage: negate-white-on-black [--fix] file-or-directory
# Without --fix will only print image filename that is assumed to be grayscale with "inverted" colormap
#

FIX=0
if [ "$1" = "--fix" ]; then
	FIX=1;
	shift;
fi

function negate(){
SRC="$1"
(echo "${SRC}"; identify -verbose -unique "${SRC}") | awk '
	BEGIN					{ isChannel = 0; isGray = 0; }
	NR == 1					{ filename = $0; }
	/Channel statistics:/	{ isChannel = 1; }
	/Colors:/				{ isChannel = 0; exit 0;}
	/Gray:/					{
								if (isChannel == 1){
									isGray = 1;
								}
							}
	/kurtosis:/				{ if (isChannel == 1) kurtosis = $2; }
    /skewness:/				{ if (isChannel == 1) skewness = $2; }
    /mean:/					{ if (isChannel == 1){
								 gsub(/[()]/, "", $3); 
								 mean = $3
								 #printf "%s %s %s\n", $0, $3, mean; 
							  }
							}
							{ next; }
	END						{
								if (isGray == 1 && mean < 0.35){
									#printf "%s %s %s %s\n", filename, mean, kurtosis, skewness;
									printf "%s\n", filename;
								}
							}
' | while read nfile; do
	echo "Found inverted file: $nfile"
	if [ $FIX = 1 ]; then
		echo "Converting: $nfile"
		cp "$nfile" "$nfile.negative"
		convert -negate "$nfile" "$nfile"
	else
		echo "Skipping: $nfile"
	fi
done
}

if [ -d "$1" ]; then
	find $1 -name '*.png' -o -name '*.jpg' | while read file; do
		negate $file
	done
else
	negate $1
fi

exit 0