What is it you want to compare about the images? If its just a question of finding identical image files stored under different filenames, you can compare crc checksums of the files.

After a quick google search, I have found a couple options. Use ImageMagick (there is a Perl module for it) or perhaps use the module Image::Compare.

I am sure there are a lot more ways but I am too lazy to list them others may be better suited to help you in this area.

 compare -metric mae image.png reference.png difference.png
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Update: I found this on Google. The shell compare returns an image with red pixels where the diff's are. Apparently, Compare in PerlMagick just returns some statistics like the following returns:

Errors is 3156.326700
Mean Error is 0.026116
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#!/usr/bin/perl
use warnings;
use strict;
use Image::Magick;

my $i1 = Image::Magick->new;
my $i2 = Image::Magick->new;

my $w = $i1->Read('image.png'); # read in images
warn("$w")  if $w;
exit  if $w =~ /^Exception/;

$w = $i2->Read( 'reference.png');
warn("$w")  if $w;
exit  if $w =~ /^Exception/;

$i1->Scale(width=>100, height=>100); # scale without preserving aspect
+ ratio
$i2->Scale(width=>100, height=>100);

$w = $i1->Compare(image=>$i2);       # compare
die "$w" if $w;

printf "Errors is %f\n",     $i1->Get('error');
printf "Mean Error is %f\n", $i1->Get('mean-error');
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UPDATE2: Found a way with the Difference option of Composite, to produce a visual diff.

#!/usr/bin/perl
use warnings;
use strict;
use Image::Magick;

my $i1 = Image::Magick->new;
my $i2 = Image::Magick->new;

#make some test files
$i1->Set(size=>'250x100');
$i1->ReadImage('xc:white');
$i1->Draw(primitive=> 'rectangle',
          fill=>'red', 
          points=>'60,30 110,70');
$i1->Write("i1.png");  #for comparison

$i2->Set(size=>'250x100');
$i2->ReadImage('xc:white');
$i2->Draw(primitive=> 'line',
          fill=>'green',
          points=>'10,10 200,100');
$i2->Write("i2.png");  #for comparison

$i1->Composite(
     gravity => "Center", 
     compose=>'Difference',
     image => $i2,
     );
$i1->Write("$0-diff-compose.png");
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#!/usr/bin/perl
use warnings;
use strict;
use Imager;

my $img = Imager->new;
$img->read(file=>'i1.png', type=>'png')
           or die "Cannot read: ", $img->errstr;

my $img1 = Imager->new;
$img1->read(file=>'i2.png', type=>'png')
           or die "Cannot read: ", $img1->errstr;

my $out = $img->difference( other => $img1 );

$out->write(file=>"$0-diff.png", type=>'png')
           or die "Cannot write: ",$out->errstr;
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The versions of perl I have do not contain those modules. That's the trick. I know there are tons of libraries out there that do this but the problem is that my toolset I have to work with is very limited.

If you can't use modules, you should look at ikegami's reply in Fast way to compare two picture-files. You will need to somehow dump the pixels manually and compare them. It will be slow in Perl.

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I'm not really a human, but I play one on earth Remember How Lucky You Are

I got the below output when tried to compare 2 png images. Cannot read: format 'png' not supported - formats bmp, ico, pnm, raw, sgi, tga available for reading Could you please help me to know the reason.

The error means that when you compiled Imager, you didn't have libpng installed on your system, so png support was skipped. Install the full libpng ( some distros separate the development headers into something like libpng-devel. Just google for libpng, compile it, install it, then rebuild Imager.

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I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku