php图片添加文字水印实现代码

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" id="codetool">