php二维码加水印图片支持ios,android,win8-PHP源码

$logo = 'logo.png';

if(is_file($logo))
{
$QR = imagecreatefromstring(file_get_contents($filename));
$logo = imagecreatefromstring(file_get_contents($logo));
$QR_width = imagesx($QR);
$QR_height = imagesy($QR);
$logo_width = imagesx($logo);
$logo_height = imagesy($logo);
$logo_qr_width = $QR_width / 5;
$scale = $logo_width / $logo_qr_width;
$logo_qr_height = $logo_height / $scale;
$from_width = ($QR_width - $logo_qr_width) / 2;
imagecopyresampled($QR, $logo, $from_width, $from_width, 0, 0, $logo_qr_width, $logo_qr_height, $logo_width, $logo_height);
imagepng($QR,$filename);
}