php如何实现pdf转换成图片

Warning
This function is currently not documented; only its argument list is available.

getImageWidth();
   $h = $imagick->getImageHeight();
   if ($w > $width || $h > $height)
   {
      if ($crop)
      {
         $imagick->cropThumbnailImage($width, $height);
      }
      else
      {
         $imagick->resizeImage($width, $height, Imagick::FILTER_LANCZOS, 1, true);
      }
   }
   $processed_image = $imagick->getImageBlob();
   return $processed_image;
}
$s=resize("123.jpg", 60, 40, 1);
echo $s;
?>

setResolution(120,120);  
   $im->setCompressionQuality(100);
   if($page==-1)   
      $im->readImage($pdf);
   else
      $im->readImage($pdf."[".$page."]");
   foreach ($im as $Key => $Var)
   {  
       $Var->setImageFormat('png');  
       $filename = $path."/". md5($Key.time()).'.png';
       if($Var->writeImage($filename) == true)
       {  
           $Return[] = $filename;  
       }  
   }  
   return $Return;  
}  
$path="images";//请确保当前目录下有这个文件夹，由于一直要用，所以就不加检测了
$s=pdf2png("test.pdf",$path);
$scount=count($s);
for($i=0;$i<$scount;$i++)
{
   echo "
Page ".($i+1)."
";
}
?>

PHP Fatal error:  Uncaught exception 'ImagickException' with message 'PostscriptDelegateFailed `test.pdf': No such file or directory'