    inline cimg_uint64& rng() { // Used as a shared global number for rng
      static cimg_uint64 rng = 0xB16B00B5U;
      return rng;
    }
    inline cimg_uint64& rng() {  
      static cimg_uint64 rng = 0xB16B00B5U;
      return rng;
    }