Compare JPGs - PERL

#!/usr/bin/perl
 
#Name: jpg_compare_diff.pl
#
#Written by: Balazs, Lendvay (ITFanatic :) )
#
#Purpose: compare two images (same size) and print the difference to a third file
#
#The script can be downloaded from "ITFanatic.com" and it is absolutely FREE,
#you can redistribute it and/or modify it under the same terms as Perl itself. (I think:) )
#This script comes with NO WARRANTY of any kind. (I am sure! :) )
#I cannot guarantee that this works in your environment, and I am not responsible
#for any harm it may cause on your computer. (I hope it won't cause harm at all :) )
 
use strict;
use GD;
use Image::Size;
 
#two input files
my $img1="p1.jpg";
my $img2="p2.jpg";
#output file
my $outfile="diff.png";
 
#determine the size of the image
my ($size_x,$size_y)=&size($img1);
print "size1: $size_x $size_y\n";
 
&compare_jpgs($img1,$img2,$outfile);
 
#this determines the size of the image
sub size()
{
	my ($img0)=@_;
	my ($size_x, $size_y) = Image::Size::imgsize($img0);
	return ($size_x,$size_y);
}
 
#this reads a jpg's rgb values
sub read_jpg()
{
	my ($img0)=@_;
	#READ RGB values
	#print "Opening image\n";
	my ($size_x0,$size_y0)=&size($img0);
	my $image = newFromJpeg GD::Image($img0) || die "Unable to open image\n";
	#my %data= ();
	foreach my $w (0..$size_x0) {
		foreach my $h (0..$size_y0) {
			my $index = $image->getPixel($w,$h);
			my ($r,$g,$b) = $image->rgb($index);
			#print RGB values
			print "RGB: ($r;$g;$b)\n";
		}
	}
}
 
#this subroutine compares the rgb values of the two images
#and prints the result to a third file
sub compare_jpgs()
{
	my ($img0,$img1,$out)=@_;
	print "Comparing $img0 and $img1\n";
 
	#determine sizes
	my ($size_x0,$size_y0)=&size($img0);
	my $image0 = newFromJpeg GD::Image($img0) || die "Unable to open image\n";
	#determine sizes
	my ($size_x1,$size_y1)=&size($img1);
	my $image1 = newFromJpeg GD::Image($img1) || die "Unable to open image\n";
	#compare the sizes and exit if they are not equal
	if (($size_x0!=$size_x1) || ($size_y0!=$size_y1)) 
	{
		print "Compare: Size does not match\n";
		exit(1);
	}
	else
	{
		print "Size matches...continuing\n";
	}
 
	#open the output file
	open OUT, ">$out" or die "Cannot open $out for write :$!";
	binmode STDOUT;
	my $image = new GD::Image($size_x, $size_y);
	my $color;
	foreach my $w (0..$size_x0) {
		foreach my $h (0..$size_y0) {
			my $index0 = $image0->getPixel($w,$h);
			#get rgb values
			my ($r0,$g0,$b0) = $image0->rgb($index0);
			#print "RGB: ($r;$g;$b)\n";
			my $index1 = $image1->getPixel($w,$h);
			#get rgb values
			my ($r1,$g1,$b1) = $image1->rgb($index1);
			#compare RGB values
			if (($r0 != $r1) || ($g0 != $g1) || ($b0 != $b1))
			{
#				print "Difference at: $w:$h pic1: ($r0,$g0,$b0) pic2: ($r1,$g1,$b1)\n";
				$color = $image->colorAllocate($r0, $g0, $b0); 
				$image->setPixel($w,$h,$color);
			}
		}
	}
	print OUT $image->png;
	close OUT;
}