/**
  * Initialize file formats supported by IMagick.
  */
 private static function initFileFormats()
 {
     if (!self::isImagickAvailable() || !(self::$file_formats = DG_Image_Editor_Imagick::query_formats())) {
         self::$file_formats = array();
     }
     $image_exts = array('jpg', 'jpeg', 'gif', 'png');
     self::$file_formats = array_map('strtolower', array_diff(self::$file_formats, $image_exts));
 }