#!/usr/bin/perl -w
use strict;

my $jpg = shift or die "$!\n";
my $data = get_file($jpg);
my @res  = sizeJPG($data);
print "$jpg width $res[0] height $res[1]\n";

sub sizeJPG {
    return unless $_[0];
    my ( $width, $height );
    ( $height, $width ) = 
   unpack( "nn", $1 ) if $_[0] =~ /\xFF\xC0...(....)/;
    return ( $width, $height );
}
    
sub get_file {
    open FILE, $_[0] or die $!;
    binmode FILE;
    local $/;
    my $data = <FILE>;
    close FILE;
    return $data;
}