       \note If true, set coordinates (n,x,y,z).
    **/
    template<typename t>
    bool contains(const T& pixel, t& n, t& x, t&y, t& z) const {
       \note If true, set coordinates (n,x,y,z).
    **/
    template<typename t>
    bool contains(const T& pixel, t& n, t& x, t&y, t& z) const {