php 给图片加水印

public function water($filename,$water,$pos=0,$pct=80){
                // 加载水印图片
                $info = $this->getImageInfo($water);
                if(!empty($info[0])){
                        $water_w = $info[0];
                        $water_h = $info[1];
                        $type = $info['type'];
                        $fun  = 'imagecreatefrom'.$type;
                        $waterimg = $fun($water);
                } else{
                        return false;
                }
                // 加载背景图片
                $info = $this->getImageInfo($this->img);
                if(!empty($info[0])){
                        $old_w = $info[0];
                        $old_h = $info[1];
                        $type  = $info['type'];
                        $fun   = 'imagecreatefrom'.$type;
                        $oldimg = $fun($this->img);
                } else{
                        return false;
                }
                // 剪切水印
                $water_w >$old_w && $water_w = $old_w;
                $water_h >$old_h && $water_h = $old_h;

                // 水印位置
                switch($pos){
                        case 0://随机
                    $posX = rand(0,($old_w - $water_w));
                    $posY = rand(0,($old_h - $water_h));
                    break;
                case 1://1为顶端居左
                    $posX = 0;
                    $posY = 0;
                    break;
                case 2://2为顶端居中
                    $posX = ($old_w - $water_w) / 2;
                    $posY = 0;
                    break;
                case 3://3为顶端居右
                    $posX = $old_w - $water_w;
                    $posY = 0;
                    break;
                case 4://4为中部居左
                    $posX = 0;
                    $posY = ($old_h - $water_h) / 2;
                    break;
                case 5://5为中部居中
                    $posX = ($old_w - $water_w) / 2;
                    $posY = ($old_h - $water_h) / 2;
                    break;
                case 6://6为中部居右
                    $posX = $old_w - $water_w;
                    $posY = ($old_h - $water_h) / 2;
                    break;
                case 7://7为底端居左
                    $posX = 0;
                    $posY = $old_h - $water_h;
                    break;
                case 8://8为底端居中
                    $posX = ($old_w - $water_w) / 2;
                    $posY = $old_h - $water_h;
                    break;
                case 9://9为底端居右
                    $posX = $old_w - $water_w;
                    $posY = $old_h - $water_h;
                    break;
                default: //随机
                    $posX = rand(0,($old_w - $water_w));
                    $posY = rand(0,($old_h - $water_h));
                    break;
                }
            // 设定图像的混色模式
                imagealphablending($oldimg, true);
                // 添加水印
                imagecopymerge($oldimg, $waterimg, $posX, $posY, 0, 0, $water_w,$water_h,$pct);
                $fun = 'image'.$type;
                !@$fun($oldimg, $filename,100) && die('保存失败!检查目录是否存在并且可写?');
                  imagedestroy($oldimg);
                  imagedestroy($waterimg);
                  return $filename;
        }