Boost C++ Libraries

boost/gil/packed_pixel.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_PACKED_PIXEL_HPP
#define BOOST_GIL_PACKED_PIXEL_HPP

#include <boost/gil/pixel.hpp>
#include <boost/gil/detail/mp11.hpp>

#include <functional>
#include <type_traits>

namespace boost { namespace gil {

/// A model of a heterogeneous pixel whose channels are bit ranges.
/// For example 16-bit RGB in '565' format.

/// \defgroup ColorBaseModelPackedPixel packed_pixel
/// \ingroup ColorBaseModel
/// \brief A heterogeneous color base whose elements are reference proxies to channels in a pixel. Models ColorBaseValueConcept. This class is used to model packed pixels, such as 16-bit packed RGB.

/// \defgroup PixelModelPackedPixel packed_pixel
/// \ingroup PixelModel
/// \brief A heterogeneous pixel used to represent packed pixels with non-byte-aligned channels. Models PixelValueConcept
///
/// Example:
/// \code
/// using rgb565_pixel_t = packed_pixel_type<uint16_t, mp11::mp_list-c<unsigned,5,6,5>, rgb_layout_t>::type;
/// static_assert(sizeof(rgb565_pixel_t) == 2, "");
///
/// rgb565_pixel_t r565;
/// get_color(r565,red_t())   = 31;
/// get_color(r565,green_t()) = 63;
/// get_color(r565,blue_t())  = 31;
/// assert(r565 == rgb565_pixel_t((uint16_t)0xFFFF));
/// \endcode

/// \ingroup ColorBaseModelPackedPixel PixelModelPackedPixel PixelBasedModel
/// \brief Heterogeneous pixel value whose channel references can be constructed from the pixel bitfield and their index. Models ColorBaseValueConcept, PixelValueConcept, PixelBasedConcept
/// Typical use for this is a model of a packed pixel (like 565 RGB)
/// \tparam BitField Type that holds the bits of the pixel. Typically an integral type, like std::uint16_t.
/// \tparam ChannelRefs MP11 list whose elements are packed channels. They must be constructible from BitField. GIL uses packed_channel_reference
/// \tparam Layout defining the color space and ordering of the channels. Example value: rgb_layout_t
template <typename BitField, typename ChannelRefs, typename Layout>
struct packed_pixel
{
    BitField _bitfield{0}; // TODO: Make private

    using layout_t = Layout;
    using value_type = packed_pixel<BitField, ChannelRefs, Layout>;
    using reference = value_type&;
    using const_reference = value_type const&;

    static constexpr bool is_mutable =
        channel_traits<mp11::mp_front<ChannelRefs>>::is_mutable;

    packed_pixel() = default;
    explicit packed_pixel(const BitField& bitfield) : _bitfield(bitfield) {}

    // Construct from another compatible pixel type
    packed_pixel(const packed_pixel& p) : _bitfield(p._bitfield) {}

    template <typename Pixel>
    packed_pixel(Pixel const& p,
        typename std::enable_if<is_pixel<Pixel>::value>::type* /*dummy*/ = nullptr)
    {
        check_compatible<Pixel>();
        static_copy(p, *this);
    }

    packed_pixel(int chan0, int chan1)
        : _bitfield(0)
    {
        static_assert(num_channels<packed_pixel>::value == 2, "");
        gil::at_c<0>(*this) = chan0;
        gil::at_c<1>(*this) = chan1;
    }

    packed_pixel(int chan0, int chan1, int chan2)
        : _bitfield(0)
    {
        static_assert(num_channels<packed_pixel>::value == 3, "");
        gil::at_c<0>(*this) = chan0;
        gil::at_c<1>(*this) = chan1;
        gil::at_c<2>(*this) = chan2;
    }

    packed_pixel(int chan0, int chan1, int chan2, int chan3)
        : _bitfield(0)
    {
        static_assert(num_channels<packed_pixel>::value == 4, "");
        gil::at_c<0>(*this) = chan0;
        gil::at_c<1>(*this) = chan1;
        gil::at_c<2>(*this) = chan2;
        gil::at_c<3>(*this) = chan3;
    }

    packed_pixel(int chan0, int chan1, int chan2, int chan3, int chan4)
        : _bitfield(0)
    {
        static_assert(num_channels<packed_pixel>::value == 5, "");
        gil::at_c<0>(*this) = chan0;
        gil::at_c<1>(*this) = chan1;
        gil::at_c<2>(*this) = chan2;
        gil::at_c<3>(*this) = chan3;
        gil::at_c<4>(*this) = chan4;
    }

    auto operator=(packed_pixel const& p) -> packed_pixel&
    {
        _bitfield = p._bitfield;
        return *this;
    }

    template <typename Pixel>
    auto operator=(Pixel const& p) -> packed_pixel&
    {
        assign(p, is_pixel<Pixel>());
        return *this;
    }

    template <typename Pixel>
    bool operator==(Pixel const& p) const
    {
        return equal(p, is_pixel<Pixel>());
    }

    template <typename Pixel>
    bool operator!=(Pixel const& p) const { return !(*this==p); }

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

    template <typename Pixel>
    void assign(Pixel const& p, std::true_type)
    {
        check_compatible<Pixel>();
        static_copy(p, *this);
    }

    template <typename Pixel>
    bool  equal(Pixel const& p, std::true_type) const
    {
        check_compatible<Pixel>();
        return static_equal(*this, p);
    }

    // Support for assignment/equality comparison of a channel with a grayscale pixel
    static void check_gray()
    {
        static_assert(std::is_same<typename Layout::color_space_t, gray_t>::value, "");
    }

    template <typename Channel>
    void assign(Channel const& channel, std::false_type)
    {
        check_gray();
        gil::at_c<0>(*this) = channel;
    }

    template <typename Channel>
    bool equal (Channel const& channel, std::false_type) const
    {
        check_gray();
        return gil::at_c<0>(*this) == channel;
    }

public:
    auto operator=(int channel) -> packed_pixel&
    {
        check_gray();
        gil::at_c<0>(*this) = channel;
        return *this;
    }

    bool operator==(int channel) const
    {
        check_gray();
        return gil::at_c<0>(*this) == channel;
    }
};

/////////////////////////////
//  ColorBasedConcept
/////////////////////////////

template <typename BitField, typename ChannelRefs, typename Layout, int K>
struct kth_element_type<packed_pixel<BitField, ChannelRefs, Layout>, K>
{
    using type = typename channel_traits<mp11::mp_at_c<ChannelRefs, K>>::value_type;
};

template <typename BitField, typename ChannelRefs, typename Layout, int K>
struct kth_element_reference_type<packed_pixel<BitField, ChannelRefs, Layout>, K>
{
    using type = typename channel_traits<mp11::mp_at_c<ChannelRefs, K>>::reference;
};

template <typename BitField, typename ChannelRefs, typename Layout, int K>
struct kth_element_const_reference_type<packed_pixel<BitField, ChannelRefs, Layout>, K>
{
    using type = typename channel_traits<mp11::mp_at_c<ChannelRefs, K>>::const_reference;
};

template <int K, typename P, typename C, typename L>
inline
auto at_c(packed_pixel<P, C, L>& p)
    -> typename kth_element_reference_type<packed_pixel<P, C, L>, K>::type
{
    return typename kth_element_reference_type
        <
            packed_pixel<P, C, L>,
            K
        >::type{&p._bitfield};
}

template <int K, typename P, typename C, typename L>
inline
auto at_c(const packed_pixel<P, C, L>& p)
    -> typename kth_element_const_reference_type<packed_pixel<P, C, L>, K>::type
{
    return typename kth_element_const_reference_type
        <
            packed_pixel<P, C, L>,
        K>::type{&p._bitfield};
}

/////////////////////////////
//  PixelConcept
/////////////////////////////

// Metafunction predicate that flags packed_pixel as a model of PixelConcept.
// Required by PixelConcept
template <typename BitField, typename ChannelRefs, typename Layout>
struct is_pixel<packed_pixel<BitField, ChannelRefs, Layout>> : std::true_type {};

/////////////////////////////
//  PixelBasedConcept
/////////////////////////////

template <typename P, typename C, typename Layout>
struct color_space_type<packed_pixel<P, C, Layout>>
{
    using type = typename Layout::color_space_t;
};

template <typename P, typename C, typename Layout>
struct channel_mapping_type<packed_pixel<P, C, Layout>>
{
    using type = typename Layout::channel_mapping_t;
};

template <typename P, typename C, typename Layout>
struct is_planar<packed_pixel<P, C, Layout>> : std::false_type {};

////////////////////////////////////////////////////////////////////////////////
/// Support for interleaved iterators over packed pixel
////////////////////////////////////////////////////////////////////////////////

/// \defgroup PixelIteratorModelPackedInterleavedPtr Pointer to packed_pixel<P,CR,Layout>
/// \ingroup PixelIteratorModel
/// \brief Iterators over interleaved pixels.
/// The pointer packed_pixel<P,CR,Layout>* is used as an iterator over interleaved
/// pixels of packed format.
/// Models PixelIteratorConcept, HasDynamicXStepTypeConcept, MemoryBasedIteratorConcept

template <typename P, typename C, typename L>
struct iterator_is_mutable<packed_pixel<P, C, L>*>
    : std::integral_constant<bool, packed_pixel<P, C, L>::is_mutable>
{};

template <typename P, typename C, typename L>
struct iterator_is_mutable<const packed_pixel<P, C, L>*> : std::false_type {};

}}  // namespace boost::gil

#endif