gistfile1.txt

  if ( $http_cookie ~* "rwdimgsize=large" ) {
    rewrite ^/(.*)/mobile/(.*)\.r(\.(?:jpe?g|png|gif))$ /$1/desktop/$2$3 last;
  }
  rewrite ^/(.*)\.r(\.(?:jpe?g|png|gif))$ /$1$2 last;