Risolto.
Ecco la classe adatta allo scopo, da sostituire a quella presente nell'image.class.php:
Codice PHP:
function SaveProportionateImage($filename, $quality, $width){
$dest_width = $width;
$ratio = $this->src_width / $dest_width;
$dest_height = $this->src_height / $ratio;
if ($dest_width >= $this->src_width){
$dest_height = $this->src_height;
$dest_width = $this->src_width;
}
$dest_image = imagecreatetruecolor( $dest_width,$dest_height);
imagecopyresampled($dest_image, $this->src_image, 0, 0, 0, 0,
$dest_width,
$dest_height,
$this->src_width,
$this->src_height);
imagejpeg($dest_image, $filename.'.jpg', $quality);
imagedestroy($dest_image);
}