    const T& minabs() const {
      if (is_empty())
        throw CImgInstanceException(_cimg_instance
                                    "minabs(): Empty instance.",
                                    cimg_instance);
      const T *ptr_minabs = _data;
      T minabs_value = *ptr_minabs;
      cimg_for(*this,ptrs,T) {
        const T ma = cimg::abs(*ptrs);
        if (ma<minabs_value) { minabs_value = ma; ptr_minabs = ptrs; }
      }
      return *ptr_minabs;
    }
    const T& minabs() const {
      if (is_empty())
        throw CImgInstanceException(_cimg_instance
                                    "minabs(): Empty instance.",
                                    cimg_instance);
      const T *ptr_minabs = _data;
      T minabs_value = *ptr_minabs;
      cimg_for(*this,ptrs,T) {
        const T ma = cimg::abs(*ptrs);
        if (ma<minabs_value) { minabs_value = ma; ptr_minabs = ptrs; }
      }
      return *ptr_minabs;
    }