PHP基于GD库的缩略图生成代码（支持jpg,gif,png格式）

还是老规矩，直接上代码

resize("tu.jpg","tu_lit.jpg",1000,1000);
echo $newimage->GetLastError();

class ImageResize{
  private $localimage;//原图路径
  private $remoteimage;//缩略图保存路径
  private $localinfo;//原图属性
  private $error;
      
  function resize($localimg, $remoteimg, $x, $y) {
    //检测是否支持gd图像处理
    if(!$this->_checkenv()){
      return false;
    }
    $this->localimage = $localimg;
    $this->remoteimage = $remoteimg;
    $this->localinfo = getimagesize($this->localimage); //获取本地图像的信息
    return $this->_resize($x,$y);
  }
  
  private function _checkenv(){
    if(!function_exists('gd_info')){
      $this->error[]="当前环境不支持GD图像处理，请先安装GD库并开启PHP相关扩展";
      return false;
    }
    return true;
  }
  
  
  private function _resize($x,$y){
    if(!$this->localinfo){
      $this->error[]="本地图像文件不存在";
      return false;
    }
    //创建图像句柄
    $im=@$this->_create($this->localinfo[2]);
    if(!$im){
      $this->error[]="当前GD库不支持图像类型：{$this->localinfo['mime']}";
      return false;
    }
    $dstsize=$this->_dstsize($x, $y);
    $dstim=@imagecreatetruecolor($dstsize["width"],$dstsize["height"]);
    $whitecolor=@imagecolorallocatealpha($dstim, 0, 0, 0,127);
    imagefill($dstim,0,0,$whitecolor);
    $re=@imagecopyresampled($dstim, $im, 0, 0, 0, 0, $dstsize["width"], $dstsize["height"], $this->localinfo[0], $this->localinfo[1]);
    if(!$re){
      $this->error[]="图像重新采样失败";
      return false;
    }
    if(!imagejpeg($dstim, $this->remoteimage)){
      if(!imagepng($dstim,$this->remoteimage)){
 if(!imagegif($dstim,$this->remoteimage)){
   $this->error[]="保存缩略图到{$this->remoteimage}失败,请检查gd环境是否正常和缩略图文件夹的写入权限。";
   return false;
 }
      }
    }
    $this->error[]="success";
    return true;
  }
  
  
  private function _create($code){
    $src=$this->localimage;
    switch ($code){
      case 1:
 return imagecreatefromgif($src);
 break;
      case 2:
 return imagecreatefromjpeg($src);
 break;
      case 3:
 return imagecreatefrompng($src);
 break;
      default :
 return false;
 break;
    }
  }
  
  
  private function _dstsize($x,$y){
    list($srcwidth,$srcheight)=$this->localinfo;
    if(($srcwidth/$srcheight)<($x/$y)){
      $x=floor($y*$srcwidth/$srcheight);
    }else{
      $y=floor($x*$srcheight/$srcwidth);
    }
    $dstsize["width"]=$x;
    $dstsize["height"]=$y;
    return $dstsize;
  }


  
  function GetLastError(){
    return array_pop($this->error);
  }
  
  
  function GetAllError(){
    return $this->error;
  }
}