这个类功能很强大，细节很棒！希望大家喜欢，并积极指点

支持文字水印、图片水印
支持水印的位置随机或固定（九宫格）
水印透明度设置（图片水印和文字水印都支持）
文字水印的字体、颜色、大小设置
图片水印的背景透明

 
<?php 
/** 
* 加水印类，支持文字图片水印的透明度设置、水印图片背景透明。 
* 日期：2011-09-27 
* 作者：www.jb51.net 
* 使用： 
* $obj = new WaterMask($imgFileName); //实例化对象 
* $obj->$waterType = 1; //类型：0为文字水印、1为图片水印 
* $obj->$transparent = 45; //水印透明度 
* $obj->$waterStr = 'www.jb51.net'; //水印文字 
* $obj->$fontSize = 16; //文字字体大小 
* $obj->$fontColor = array(255,0255); //水印文字颜色（RGB） 
* $obj->$fontFile = = 'AHGBold.ttf'; //字体文件 
* $obj->output(); //输出水印图片文件覆盖到输入的图片文件 
*/ 
class WaterMask{ 
public $waterType = 1; //水印类型：0为文字水印、1为图片水印 
public $pos = 0; //水印位置 
public $transparent = 45; //水印透明度 

public $waterStr = 'www.jb51.net'; //水印文字 
public $fontSize = 16; //文字字体大小 
public $fontColor = array(255,0,255); //水印文字颜色（RGB） 
public $fontFile = 'AHGBold.ttf'; //字体文件 

public $waterImg = 'logo.png'; //水印图片 

private $srcImg = ''; //需要添加水印的图片 
private $im = ''; //图片句柄 
private $water_im = ''; //水印图片句柄 
private $srcImg_info = ''; //图片信息 
private $waterImg_info = ''; //水印图片信息 
private $str_w = ''; //水印文字宽度 
private $str_h = ''; //水印文字高度 
private $x = ''; //水印X坐标 
private $y = ''; //水印y坐标 

function __construct($img) { //析构函数 
$this->srcImg = file_exists($img) ? $img : die('"'.$img.'" 源文件不存在！'); 
} 
private function imginfo() { //获取需要添加水印的图片的信息，并载入图片。 
$this->srcImg_info = getimagesize($this->srcImg); 
switch ($this->srcImg_info[2]) { 
case 3: 
$this->im = imagecreatefrompng($this->srcImg); 
break 1; 
case 2: 
$this->im = imagecreatefromjpeg($this->srcImg); 
break 1; 
case 1: 
$this->im = imagecreatefromgif($this->srcImg); 
break 1; 
default: 
die('原图片（'.$this->srcImg.'）格式不对，只支持PNG、JPEG、GIF。'); 
} 
} 
private function waterimginfo() { //获取水印图片的信息，并载入图片。 
$this->waterImg_info = getimagesize($this->waterImg); 
switch ($this->waterImg_info[2]) { 
case 3: 
$this->water_im = imagecreatefrompng($this->waterImg); 
break 1; 
case 2: 
$this->water_im = imagecreatefromjpeg($this->waterImg); 
break 1; 
case 1: 
$this->water_im = imagecreatefromgif($this->waterImg); 
break 1; 
default: 
die('水印图片（'.$this->srcImg.'）格式不对，只支持PNG、JPEG、GIF。'); 
} 
} 
private function waterpos() { //水印位置算法 
switch ($this->pos) { 
case 0: //随机位置 
$this->x = rand(0,$this->srcImg_info[0]-$this->waterImg_info[0]); 
$this->y = rand(0,$this->srcImg_info[1]-$this->waterImg_info[1]); 
break 1; 
case 1: //上左 
$this->x = 0; 
$this->y = 0; 
break 1; 
case 2: //上中 
$this->x = ($this->srcImg_info[0]-$this->waterImg_info[0])/2; 
$this->y = 0; 
break 1; 
case 3: //上右 
$this->x = $this->srcImg_info[0]-$this->waterImg_info[0]; 
$this->y = 0; 
break 1; 
case 4: //中左 
$this->x = 0; 
$this->y = ($this->srcImg_info[1]-$this->waterImg_info[1])/2; 
break 1; 
case 5: //中中 
$this->x = ($this->srcImg_info[0]-$this->waterImg_info[0])/2; 
$this->y = ($this->srcImg_info[1]-$this->waterImg_info[1])/2; 
break 1; 
case 6: //中右 
$this->x = $this->srcImg_info[0]-$this->waterImg_info[0]; 
$this->y = ($this->srcImg_info[1]-$this->waterImg_info[1])/2; 
break 1; 
case 7: //下左 
$this->x = 0; 
$this->y = $this->srcImg_info[1]-$this->waterImg_info[1]; 
break 1; 
case 8: //下中 
$this->x = ($this->srcImg_info[0]-$this->waterImg_info[0])/2; 
$this->y = $this->srcImg_info[1]-$this->waterImg_info[1]; 
break 1; 
default: //下右 
$this->x = $this->srcImg_info[0]-$this->waterImg_info[0]; 
$this->y = $this->srcImg_info[1]-$this->waterImg_info[1]; 
break 1; 
} 
} 
private function waterimg() { 
if ($this->srcImg_info[0] <= $this->waterImg_info[0] || $this->srcImg_info[1] <= $this->waterImg_info[1]){ 
die('水印比原图大！'); 
} 
$this->waterpos(); 
$cut = imagecreatetruecolor($this->waterImg_info[0],$this->waterImg_info[1]); 
imagecopy($cut,$this->im,0,0,$this->x,$this->y,$this->waterImg_info[0],$this->waterImg_info[1]); 
$pct = $this->transparent; 
imagecopy($cut,$this->water_im,0,0,0,0,$this->waterImg_info[0],$this->waterImg_info[1]); 
imagecopymerge($this->im,$cut,$this->x,$this->y,0,0,$this->waterImg_info[0],$this->waterImg_info[1],$pct); 
} 
private function waterstr() { 
$rect = imagettfbbox($this->fontSize,0,$this->fontFile,$this->waterStr); 
$w = abs($rect[2]-$rect[6]); 
$h = abs($rect[3]-$rect[7]); 
$fontHeight = $this->fontSize; 
$this->water_im = imagecreatetruecolor($w, $h); 
imagealphablending($this->water_im,false); 
imagesavealpha($this->water_im,true); 
$white_alpha = imagecolorallocatealpha($this->water_im,255,255,255,127); 
imagefill($this->water_im,0,0,$white_alpha); 
$color = imagecolorallocate($this->water_im,$this->fontColor[0],$this->fontColor[1],$this->fontColor[2]); 
imagettftext($this->water_im,$this->fontSize,0,0,$this->fontSize,$color,$this->fontFile,$this->waterStr); 
$this->waterImg_info = array(0=>$w,1=>$h); 
$this->waterimg(); 
} 
function output() { 
$this->imginfo(); 
if ($this->waterType == 0) { 
$this->waterstr(); 
}else { 
$this->waterimginfo(); 
$this->waterimg(); 
} 
switch ($this->srcImg_info[2]) { 
case 3: 
imagepng($this->im,$this->srcImg); 
break 1; 
case 2: 
imagejpeg($this->im,$this->srcImg); 
break 1; 
case 1: 
imagegif($this->im,$this->srcImg); 
break 1; 
default: 
die('添加水印失败！'); 
break; 
} 
imagedestroy($this->im); 
imagedestroy($this->water_im); 
} 
} 
?>