gistfile1.txt

location ~* \.r\.(jpe?g|png|gif) {
  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;
  access_log off;
  try_files $uri @cache;
}