php生成水印，包括位置和透明度(8)

                    $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