header("content-type:image/jpg");

  import('ORG.Util.Image');

  $Image = new Image();

$Image->water('./public/upload/b.jpg','./public/upload/2.jpg',1);

  }  

这里的路径不能写成__ROOT__/public/upload/b.jpg

./表示当前项目的入口文件

这里扩展了打水印的位置，

switch($position)
        {
            case 9://9为底端居右
            $posX = $ground_w - $w;
            $posY = $ground_h - $h;
            break;
            case 0://随机
            $posX = rand(0,($ground_w - $w));
            $posY = rand(0,($ground_h - $h));
            break;
            case 1://1为顶端居左
            $posX = 0;
            $posY = 0;
            break;
            case 2://2为顶端居中
            $posX = ($ground_w - $w) / 2;
            $posY = 0;
            break;
            case 3://3为顶端居右
            $posX = $ground_w - $w;
            $posY = 0;
            break;
            case 4://4为中部居左
            $posX = 0;
            $posY = ($ground_h - $h) / 2;
            break;
            case 5://5为中部居中
            $posX = ($ground_w - $w) / 2;
            $posY = ($ground_h - $h) / 2;
            break;
            case 6://6为中部居右
            $posX = $ground_w - $w;
            $posY = ($ground_h - $h) / 2;
            break;
            case 7://7为底端居左
            $posX = 0;
            $posY = $ground_h - $h;
            break;
            case 8://8为底端居中
            $posX = ($ground_w - $w) / 2;
            $posY = $ground_h - $h;
            break;
             
            default://随机位置
            $posX = rand(0,($ground_w - $w));
            $posY = rand(0,($ground_h - $h));
            break;
        }
在官方源码的基础上做的改进