Pimcore\Model\Asset\Image::getThumbnail PHP Method

    public function getThumbnail($config = null, $deferred = true)
    {
        return new Image\Thumbnail($this, $config, $deferred);
    }

 /**
  * @param $conf
  * @return Asset\Image\Thumbnail|string
  */
 public function getThumbnail($conf)
 {
     if ($this->image instanceof Asset) {
         $thumbConfig = $this->image->getThumbnailConfig($conf);
         if ($thumbConfig && $this->cropPercent) {
             $thumbConfig->addItemAt(0, "cropPercent", array("width" => $this->cropWidth, "height" => $this->cropHeight, "y" => $this->cropTop, "x" => $this->cropLeft));
             $hash = md5(Serialize::serialize($thumbConfig->getItems()));
             $thumbConfig->setName($thumbConfig->getName() . "_auto_" . $hash);
         }
         return $this->image->getThumbnail($thumbConfig);
     }
     return "";
 }