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

sub image_size {
  return unless $_[0];
    my ($width, $height, $sig);
    if ( $_[0] =~ m/^GIF8..(....)/s ) {
        $sig = 'GIF';        # found GIF signature
        ($width, $height) = unpack( "SS", $1 );
    }
    elsif ( $_[0] =~ m/^^\xFF\xD8.{4}JFIF/s  ) {
        $sig = 'JPEG';        # found JPG signature
        ($height,$width) = unpack( "nn", $1 ) if $_[0] =~ /\xFF\xC0...(....)/s;
    }
    elsif ( $_[0] =~ /^\x89PNG\x0d\x0a\x1a\x0a/  ) {
        $sig = 'PNG';        # found PNG signature
        ($width, $height) = unpack( "NN", $1 ) if $_[0] =~ /IHDR(.{8})/s;
    }
    elsif ( $_[0] =~ /BM.{16}(.{8})/s ) {
        $sig = 'BMP';        # found bitmap sig
        ($width, $height) = unpack( "LL", $1);
    }
  return $width, $height, $sig;
}

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


for my $img ( qw( c:/sample.bmp c:/sample.jpg c:/sample.gif c:/sample.png) ) {
    my $data = get_file($img);
    my @res = image_size($data);
    print "$img $res[2] width $res[0] height $res[1]\n";
}
__END__
c:/sample.bmp BMP width 512 height 384
c:/sample.jpg JPEG width 100 height 149
c:/sample.gif GIF width 110 height 58
c:/sample.png PNG width 256 height 192