Codice PHP:
$src imagecreatefromjpeg($_SERVER['DOCUMENT_ROOT'].'/image.jpg');
$logo imagecreatefrompng($_SERVER['DOCUMENT_ROOT'].'/logo.png');
imagecopy($src$logo101000imagesx($logo), imagesy($logo));
imagedestroy($logo);

header("Content-type: image/jpeg");
imagejpeg($src);