php生成水印，包括位置和透明度(7)

                        $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;