php类库给现有的图片加文字水印，代码不是很完善，欢迎大家多多指教！代码如下：

<?php

/*PHP图片加文字水印类库

  QQ:3697578482 伤心的歌

  该类库暂时只支持文字水印，位置为右下角，颜色随机

 调用方法：
   1、在需要加水印的文件顶部引入类库：
      include_once 'imageClass.php';
   2、声明新类：
      $tpl=new image_fu;
   3、给图片水印提供参数：
      $tpl->img(图片路径,水印文字,字体路径,字体大小,字体角度);
      比如：$tpl->img('abc.jpg','这是水印文字','ziti.ttf',30,0)

*/

 class image_fu{

     private $image;
     private $img_info;
     private $img_width;
     private $img_height;
     private $img_im;
     private $img_text;
     private $img_ttf='';
     private $img_new;
     private $img_text_size;
     private $img_jd;

     function img($img='',$txt='',$ttf='',$size=12,$jiaodu=0){
        if(isset($img)&&file_exists($img)){//检测图片是否存在
           $this->image   =$img; 
           $this->img_text=$txt;
           $this->img_text_size=$size;
           $this->img_jd=$jiaodu;
          if(file_exists($ttf)){
           $this->img_ttf=$ttf;
          }else{
           exit('字体文件：'.$ttf.'不存在！'); 
          }
           $this->imgyesno();
        }else{
          exit('图片文件:'.$img.'不存在');
       } 
     }

     private function imgyesno(){

        $this->img_info  =getimagesize($this->image);
        $this->img_width =$this->img_info[0];//图片宽
        $this->img_height=$this->img_info[1];//图片高

        //检测图片类型
        switch($this->img_info[2]){
             case 1:$this->img_im = imagecreatefromgif($this->image);break; 
             case 2:$this->img_im = imagecreatefromjpeg($this->image);break; 
             case 3:$this->img_im = imagecreatefrompng($this->image);break; 
             default:exit('图片格式不支持水印'); 
        }

           $this->img_text();
     }

     private function img_text(){

         imagealphablending($this->img_im,true);

         //设定颜色
          $color=imagecolorallocate($this->img_im,rand(0,255),rand(0,255),rand(0,255));
          $txt_height=$this->img_text_size;
          $txt_jiaodu=$this->img_jd;
          $ttf_im=imagettfbbox($txt_height,$txt_jiaodu,$this->img_ttf,$this->img_text);
          $w = $ttf_im[2] - $ttf_im[6]; 
          $h = $ttf_im[3] - $ttf_im[7]; 
          //$w = $ttf_im[7]; 
          //$h = $ttf_im[8]; 

          unset($ttf_im);

          $txt_y     =$this->img_height-$h;
          $txt_x     =$this->img_width-$w;
          //$txt_y     =0;
          //$txt_x     =0;

          $this->img_new=@imagettftext($this->img_im,$txt_height,$txt_jiaodu,$txt_x,$txt_y,$color,$this->img_ttf,$this->img_text);

         @unlink($this->image);//删除图片
        switch($this->img_info[2]) {//取得背景图片的格式 
          case 1:imagegif($this->img_im,$this->image);break; 
          case 2:imagejpeg($this->img_im,$this->image);break; 
          case 3:imagepng($this->img_im,$this->image);break; 
          default: exit('水印图片失败'); 
        } 

     }

     //显示图片
     function img_show(){echo '<img src="'.$this->image.'" border="0" alt="'.$this->img_text.'" />';}

     //释放内存
     private function img_nothing(){
         unset($this->img_info); 
         imagedestroy($this->img_im); 
     }

 }

?>