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 <boost/mpl/range_c.hpp>
#include <boost/mpl/vector_c.hpp>

// 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)

template <typename ChannelReference, // Models ChannelConcept. A channel reference, unsigned char& or const unsigned char&
          typename Layout>           // A layout (includes the color space and channel ordering)
struct interleaved_ref {
private:
    typedef typename channel_traits<ChannelReference>::value_type      channel_t;
    typedef typename channel_traits<ChannelReference>::reference       channel_reference_t;
    typedef typename channel_traits<ChannelReference>::const_reference channel_const_reference_t;
    typedef typename channel_traits<ChannelReference>::pointer         channel_pointer_t;
public:
// Required by ColorBaseConcept
    typedef Layout layout_t;

    // 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
    typedef pixel<channel_t, layout_t> value_type;
    typedef interleaved_ref            reference;
    typedef interleaved_ref<channel_const_reference_t, layout_t> const_reference;
    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> {
    typedef ChannelReference type;
};

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

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


// 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 boost::mpl::true_ {};


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

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

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

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

} }  // namespace boost::gil

#endif