php加水印的代码(支持半透明透明打水印，支持png透明背景)

一个简单的打水印代码（图片水印），支持水印透明度设置，也支持png透明背景格式图片打水印

//原始图像 
       $dst = "/upload/20120914/20120914040740-0.jpg"; //注意图片路径要正确 
       //得到原始图片信息 
       $dst_info = getimagesize($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,$dst);break; 
        default: 
        die("不支持的文件类型2");exit; 
       } 
       imagedestroy($dst_im); 
       imagedestroy($src_im);