    CImg<T>& operator*=(const t value) {
      if (is_empty()) return *this;
      cimg_openmp_for(*this,*ptr * value,262144);
      return *this;
    }
    CImg<T>& operator*=(const t value) {
      if (is_empty()) return *this;
      cimg_openmp_for(*this,*ptr * value,262144);
      return *this;
    }