#!/usr/bin/perl -w
use strict;
##</code><code>##

use warnings;

##</code><code>##

my $data = get_file($jpg);
my @res  = sizeJPG($data);
print "$jpg width $res[0] height $res[1]\n";
##</code><code>##

my $data = get_file($jpg);
my ($h,$v)  = sizeJPG($data);
print "$jpg width $h height $v\n";
##</code><code>##

sub sizeJPG {
    return unless $_[0];
    my ( $width, $height );
    ( $height, $width ) = 
   unpack( "nn", $1 ) if $_[0] =~ /\xFF\xC0...(....)/;
    return ( $width, $height );
}
##</code><code>##

local $_=shift;

##</code><code>##

my ($width,$height)=unpack "nn", (/\xFF\xC0...(....)/)[0];

##</code><code>##

my ($width,$height)=unpack "nn", /\xFF\xC0...(....)/ ? $1 : '';
# or "\0" x 4, maybe?

##</code><code>##

sub get_file {
    open FILE, $_[0] or die $!;
    binmode FILE;
    local $/;
    my $data = <FILE>;
    close FILE;
    return $data;
}
##</code><code>##

sub get_file {
    local $/;
    open my $fh, '<:raw', shift or die $!;
    <$fh>;
}