Resize image only when it is too big

[eluser]Bramme[/eluser]
you'll have to do the calculations yourself...

Code:

$image_url = '/myimage.jpg';
$max_size = 500px;

list($width, $height, $t, $i) = getimagesize($image_url);
if($width > $max_size || $height > $max_size) {
    // use image lib
}