boost::gil::channel_traits

template<typename T>
struct channel_traits
    : detail::channel_traits_impl<T, std::is_class<T>::value>

template <typename Channel>
struct channel_traits {
    using value_type = ...;
    using reference = ...;
    using pointer = ...;
    using const_reference = ...;
    using const_pointer = ...;

    static const bool is_mutable;
    static value_type min_value();
    static value_type max_value();
};