Call to undefined function imagecreatefrom() 出现这样的报错

<?php
class image{
 
    private $info;
	private $image;
    //打开图片
    public function __construct($src){
    //图片信息 
    $info=getimagesize($src);
    $this->info=array(
	   'width'=>$info[0],
	   'height'=>$info[1],
	   'type'=>image_type_to_extension($this->info[2],false),
       'mime'=>$info['mime']
    );
    $fun="imagecreatefrom{$this->info['type']}";
    $this->image=$fun($src);
   } 

   //压缩操作
   public function thumb($width,$height){
       $image_thumb=imagecreatetruecolor($width,$height);
       imagecopyresampled($image_thumb,$this->image,0,0,0,0,$width,$height,$this->info['width'],$this->info['height']);
       imagedestroy($this->image);
	   $this->image=$image_thumb;
   }

  //输出图片到浏览器
   public function show(){
     header("Content-type:".$this->info['mime']);
	 $func="image{$this->info['type']}";
	 $func($this->image);
 }
 //保存到硬盘中
  public function save($newname){
     $func="image{$this->info['type']}";
	 $func($this->image,$newname.'.'.$this->info['type']);
  }
  //销毁图片
  public function __destruct(){
   imagedestroy($this->image);
  }
  }
?>

Fatal error: Call to undefined function imagecreatefrom() in D:\phpStudy\WWW\web\image.class.php on line 17