gil/example/interleaved_ref.hpp

//
// Copyright 2005-2007 Adobe Systems Incorporated
//
// Distributed under the Boost Software License, Version 1.0
// See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt
//
#ifndef BOOST_GIL_EXAMPLE_INTERLEAVED_REF_HPP
#define BOOST_GIL_EXAMPLE_INTERLEAVED_REF_HPP

#include <boost/gil/extension/dynamic_image/dynamic_image_all.hpp>

#include <type_traits>

// Example on how to create a new model of a pixel reference

namespace boost { namespace gil {

// A model of an interleaved pixel reference. Holds a pointer to the first channel
// MODELS:
//    MutableHomogeneousPixelConcept
//       MutableHomogeneousColorBaseConcept
//           MutableColorBaseConcept
//           HomogeneousColorBaseConcept
//               ColorBaseConcept
//    HomogeneousPixelBasedConcept
//       PixelBasedConcept
//
// For planar reference proxies to work properly, all of their methods must be const-qualified
// and their iterator's reference type must be const-qualified.
// Mutability of the reference proxy is part of its type (in this case, depends on the mutability of ChannelReference)

/// \tparam ChannelReference - Models ChannelConcept.
///         A channel reference, unsigned char& or const unsigned char&
/// \tparam Layout - A layout (includes the color space and channel ordering)
template <typename ChannelReference, typename Layout>
struct interleaved_ref
{
private:
    using channel_t = typename channel_traits<ChannelReference>::value_type;
    using channel_pointer_t = typename channel_traits<ChannelReference>::pointer;
    using channel_reference_t = typename channel_traits<ChannelReference>::reference;
    using channel_const_reference_t = typename channel_traits<ChannelReference>::const_reference;

public:
    using layout_t = Layout; // Required by ColorBaseConcept

    // Copy construction from a compatible type. The copy constructor of references is shallow. The channels themselves are not copied.
    interleaved_ref(const interleaved_ref& p) : _channels(p._channels) {}
    template <typename P> interleaved_ref(const P& p) : _channels(p._channels) { check_compatible<P>(); }

    template <typename P> bool operator==(const P& p)    const { check_compatible<P>(); return static_equal(*this,p); }
    template <typename P> bool operator!=(const P& p)    const { return !(*this==p); }

// Required by MutableColorBaseConcept

    // Assignment from a compatible type
    const interleaved_ref&  operator=(const interleaved_ref& p)  const { static_copy(p,*this); return *this; }
    template <typename P> const interleaved_ref& operator=(const P& p) const { check_compatible<P>(); static_copy(p,*this); return *this; }

// Required by PixelConcept
    using value_type = pixel<channel_t, layout_t>;
    using reference = interleaved_ref;
    using const_reference = interleaved_ref<channel_const_reference_t, layout_t>;
    static const bool is_mutable = channel_traits<ChannelReference>::is_mutable;

// Required by HomogeneousPixelConcept
    ChannelReference                   operator[](std::size_t i) const { return _channels[i]; }

// Custom constructor (not part of any concept)
    explicit interleaved_ref(channel_pointer_t channels) : _channels(channels) {}
// This is needed for the reference proxy to work properly
    const interleaved_ref*             operator->()              const { return this; }
private:
    channel_pointer_t _channels;

    template <typename Pixel> static void check_compatible() { gil_function_requires<PixelsCompatibleConcept<Pixel,interleaved_ref>>(); }
};

// Required by ColorBaseConcept
template <typename ChannelReference, typename Layout, int K>
struct kth_element_type<interleaved_ref<ChannelReference, Layout>, K>
{
    using type = ChannelReference;
};

template <typename ChannelReference, typename Layout, int K>
struct kth_element_reference_type<interleaved_ref<ChannelReference, Layout>, K>
{
    using type = ChannelReference;
};

template <typename ChannelReference, typename Layout, int K>
struct kth_element_const_reference_type<interleaved_ref<ChannelReference, Layout>, K>
{
    using type = ChannelReference;
    // XXX: using type = typename channel_traits<ChannelReference>::const_reference;
};

// Required by ColorBaseConcept
template <int K, typename ChannelReference, typename Layout>
typename element_reference_type<interleaved_ref<ChannelReference,Layout>>::type
at_c(const interleaved_ref<ChannelReference,Layout>& p) { return p[K]; };

// Required by HomogeneousColorBaseConcept
template <typename ChannelReference, typename Layout>
typename element_reference_type<interleaved_ref<ChannelReference,Layout>>::type
dynamic_at_c(const interleaved_ref<ChannelReference,Layout>& p, std::size_t n) { return p[n]; };

namespace detail {
    struct swap_fn_t {
        template <typename T> void operator()(T& x, T& y) const {
            using std::swap;
            swap(x,y);
        }
    };
}

// Required by MutableColorBaseConcept. The default std::swap does not do the right thing for proxy references - it swaps the references, not the values
template <typename ChannelReference, typename Layout>
void swap(const interleaved_ref<ChannelReference,Layout>& x, const interleaved_ref<ChannelReference,Layout>& y) {
    static_for_each(x,y,detail::swap_fn_t());
};

// Required by PixelConcept
template <typename ChannelReference, typename Layout>
struct is_pixel<interleaved_ref<ChannelReference,Layout>> : public std::true_type {};


// Required by PixelBasedConcept
template <typename ChannelReference, typename Layout>
struct color_space_type<interleaved_ref<ChannelReference, Layout>>
{
    using type = typename Layout::color_space_t;
};

// Required by PixelBasedConcept
template <typename ChannelReference, typename Layout>
struct channel_mapping_type<interleaved_ref<ChannelReference, Layout>>
{
    using type = typename Layout::channel_mapping_t;
};

// Required by PixelBasedConcept
template <typename ChannelReference, typename Layout>
struct is_planar<interleaved_ref<ChannelReference,Layout>> : std::false_type {};

// Required by HomogeneousPixelBasedConcept
template <typename ChannelReference, typename Layout>
struct channel_type<interleaved_ref<ChannelReference, Layout>>
{
    using type = typename channel_traits<ChannelReference>::value_type;
};

} }  // namespace boost::gil

#endif