PHP实现的给图片添加水印功能，可添加文字水印或图片水印，使用文字水印时需要提供字体文件，使用图片水印时需要提供水印图片，水印图片不能比要添加水印的图片大，请使用背景透明的水印图片。
该水印类支持自定义水印位置、自定义水印大小和水印的透明度，字体水印可自定义颜色等，功能已相应完善。
完整源代码如下(注解中已给出使用示例)：
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);
}
}
?>
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