/**
  * Returns true if sfFilebasePluginFile is an
  * image file. Used to factory
  * a sfFilebasePluginImage instance by sfFilebasePlugin::
  * getFilebaseFile()
  *
  * @see sfFilebaseUtil::getIsImage()
  * @todo improved mime-type detection
  * @return boolean true if file is an image
  */
 public function isImage()
 {
     return $this->filebase->getIsImage($this);
 }