public function scale($scl)
{
// Determine the new width and height of the image based on the
// value of the $scl argument.
$this->setImageInfo();
$wid = round($this->width * $scl);
$hgt = round($this->height * $scl);
// Create a new image output resource.
$this->resource->resizeImage($wid, $hgt, $this->filter, $this->blur);
$this->setImageInfo();
return $this;
}