/**
  *
  *
  * @param string  $src
  * @param int     $w
  * @param int     $h
  * @param string  $crop
  * @return string
  */
 private static function get_retina_file_name_relative_to_content($src, $mult = 2)
 {
     $path_parts = pathinfo($src);
     $dir_relative_to_content = TimberImageHelper::get_directory_relative_to_content($src);
     $newbase = $path_parts['filename'] . '@' . $mult . 'x';
     // add @2x, @3x, @1.5x, etc.
     $new_name = $newbase . '.' . $path_parts['extension'];
     return $dir_relative_to_content . '/' . $new_name;
 }