/**
* Resize an image and keep the proportions
* @author Allison Beckwith <allison@planetargon.com>
* @param string $filename
* @param integer $max_width
* @param integer $max_height
* @return image
*/
function resizeImage($filename, $max_width, $max_height)
{
   list($orig_width, $orig_height) = getimagesize($filename);
   $width = $orig_width;
   $height = $orig_height;
   # taller
   if ($height > $max_height) {
       $width = ($max_height / $height) * $width;
       $height = $max_height;
   }
   # wider
   if ($width > $max_width) {
       $height = ($max_width / $width) * $height;
       $width = $max_width;
   }
   $image_p = imagecreatetruecolor($width, $height);
   $image = imagecreatefromjpeg($filename);
   imagecopyresampled($image_p, $image, 0, 0, 0, 0, 
                                    $width, $height, $orig_width, $orig_height);
   return $image_p;
}