php水印代码，php半透明水印支持png透明背景

//原始图像
$dst = "/upload/20140914/20120914040740-0.jpg"; //图片路径

//原始图片信息
$dst_info = getimagesize($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("不支持的文件类型1");exit;
}
//水印图像
$src = "/images/shuiyin.png"; //注意路径要写对
$src_info = getimagesize($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("不支持的文件类型1");exit;
}
//半透明格式水印
//$alpha = 50; //水印透明度
//imagecopymerge($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);
//支持png本身透明度的方式
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]);

//保存图片
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("不支持的文件类型2");exit;
}

//销毁gd库对象
imagedestroy($dst_im);
imagedestroy($src_im);