/**
* 為圖片添加水印
* @static public
* @param string $source 原文件名
* @param string $water 水印圖片
* @param string $$savename 添加水印后的圖片名
* @param string $postion 水印的具體位置 leftbottom rightbottom lefttop righttop center <新增>
* @param string $alpha 水印的透明度
* @return void
*/
static public function water($source, $water, $savename=null,$postion="center", $alpha=80) {
//檢查文件是否存在
if (!file_exists($source) || !file_exists($water))
return false;
//圖片信息
$sInfo = self::getImageInfo($source);
$wInfo = self::getImageInfo($water);
//如果圖片小于水印圖片，不生成圖片
if ($sInfo["width"] < $wInfo["width"] || $sInfo['height'] < $wInfo['height']) return false; //建立圖像 $sCreateFun = "imagecreatefrom" . $sInfo['type']; $sImage = $sCreateFun($source); $wCreateFun = "imagecreatefrom" . $wInfo['type']; $wImage = $wCreateFun($water); //設(shè)定圖像的混色模式 imagealphablending($wImage, true); //圖像位置,默認(rèn)為右下角右對(duì)齊 $posArr = $this->WaterPostion($postion,$sInfo,$wInfo); //新增
  //生成混合圖像
  imagecopymerge($sImage, $wImage, $posArr[0], $posArr[1], 0, 0, $wInfo['width'], $wInfo['height'], $alpha);
  //輸出圖像
  $ImageFun = 'Image' . $sInfo['type'];
 //如果沒(méi)有給出保存文件名，默認(rèn)為原圖像名
 if (!$savename) {
   $savename = $source;
   @unlink($source);
  }
 //保存圖像
  $ImageFun($sImage, $savename);
   imagedestroy($sImage);
 }
 private function WaterPostion($postion,$sInfo,$wInfo)
 {
   $posY = $sInfo["height"] - $wInfo["height"];
   $posX = $sInfo["width"] - $wInfo["width"];
  switch($postion)
 {
   case "rightbottom":
    return array($posX,$posY);
   break;
   case "leftbottom":
    return array($wInfo["width"],$posY);
   break;
   case "lefttop":
    return array($wInfo["width"],$wInfo["height"]);
   break;
   case "righttop":
    return array($posX,$wInfo["height"]);
   break;
   case "center":
    return array($posX/2,$posY/2);
  break;
  }
}