use GD;

open(IMAGE, 'foo.jpg') 
    or die("Can't open foo.jpg: $!");

my $im = newFromJpeg GD::Image(IMAGE) 
    or die("Can't create image from foo.jpg: $!");

my ($w,$h) = $im->getBounds();

close(IMAGE);

print "foo.jpg is $w x $h\n";
^d
foo.jpg is 1024 x 768