PHP watermark code, PHP translucent watermark supports png transparent background

//Original image
$dst = "/upload/20140914/20120914040740-0.jpg"; //Picture path
//Original picture information
$dst_info = getimagesize($dst);
switch ($dst_info[2])
{
case 1:
$dst_im =imagecreatefromgif($dst);break;
case 2:
$dst_im =imagecreatefromjpeg($dst) ;break;
case 3:
$dst_im =imagecreatefrompng($dst);break;
case 6:
$dst_im =imagecreatefromwbmp($dst);break;
default:
die("Unsupported file type 1") ;exit;
}
//Watermark image
$src = "/images/shuiyin.png"; //Note that the path must be written correctly
$src_info = getimagesize($src);
switch ($src_info[2])
 {
case 1:
$src_im =imagecreatefromgif($src);break;
case 2:
$src_im =imagecreatefromjpeg($src);break;
case 3:
$src_im =imagecreatefrompng($src);break;
 case 6:
$src_im =imagecreatefromwbmp($src);break;
default:
die("Unsupported file type 1");exit;
}
//Semi-transparent format watermark
//$alpha = 50; //Watermark transparency
//imagecopymerge($dst_im,$src_im,$dst_info[0]-$src_info[0]-10,$dst_info[1]-$src_info[1]-10,0,0,$src_info[ 0],$src_info[1],$alpha);
//How to support the transparency of png itself
imagecopy($dst_im,$src_im,$dst_info[0]-$src_info[0]-10,$dst_info[1] -$src_info[1]-10,0,0,$src_info[0],$src_info[1]);
//Save the picture
switch ($dst_info[2]){
case 1:
imagegif($dst_im,$dst);break;
case 2:
imagejpeg($dst_im,$dst);break;
case 3:
imagepng($dst_im,$dst);break;
case 6:
imagewbmp($dst_im,$dst);break;
default:
die("Unsupported file type 2");exit;
}
//Destroy the gd library object
imagedestroy($dst_im);
imagedestroy($src_im);