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Editing: bit_aligned_pixel_reference.hpp
// // Copyright 2005-2007 Adobe Systems Incorporated // Copyright 2019 Mateusz Loskot <mateusz at loskot dot net> // // 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_BIT_ALIGNED_PIXEL_REFERENCE_HPP #define BOOST_GIL_BIT_ALIGNED_PIXEL_REFERENCE_HPP #include <boost/gil/pixel.hpp> #include <boost/gil/channel.hpp> #include <boost/gil/detail/mp11.hpp> #include <boost/assert.hpp> #include <boost/config.hpp> #include <functional> #include <type_traits> namespace boost { namespace gil { /// A model of a heterogeneous pixel that is not byte aligned. /// Examples are bitmap (1-bit pixels) or 6-bit RGB (222). ///////////////////////////// // bit_range // // Represents a range of bits that can span multiple consecutive bytes. The range has a size fixed at compile time, but the offset is specified at run time. ///////////////////////////// template <int RangeSize, bool IsMutable> class bit_range { public: using byte_t = mp11::mp_if_c<IsMutable, unsigned char, unsigned char const>; using difference_type = std::ptrdiff_t; template <int RS, bool M> friend class bit_range; private: byte_t* _current_byte; // the starting byte of the bit range int _bit_offset; // offset from the beginning of the current byte. 0<=_bit_offset<=7 public: bit_range() : _current_byte(nullptr), _bit_offset(0) {} bit_range(byte_t* current_byte, int bit_offset) : _current_byte(current_byte) , _bit_offset(bit_offset) { BOOST_ASSERT(bit_offset >= 0 && bit_offset < 8); } bit_range(const bit_range& br) : _current_byte(br._current_byte), _bit_offset(br._bit_offset) {} template <bool M> bit_range(const bit_range<RangeSize,M>& br) : _current_byte(br._current_byte), _bit_offset(br._bit_offset) {} bit_range& operator=(const bit_range& br) { _current_byte = br._current_byte; _bit_offset=br._bit_offset; return *this; } bool operator==(const bit_range& br) const { return _current_byte==br._current_byte && _bit_offset==br._bit_offset; } bit_range& operator++() { _current_byte += (_bit_offset+RangeSize) / 8; _bit_offset = (_bit_offset+RangeSize) % 8; return *this; } bit_range& operator--() { bit_advance(-RangeSize); return *this; } void bit_advance(difference_type num_bits) { int new_offset = int(_bit_offset+num_bits); _current_byte += new_offset / 8; _bit_offset = new_offset % 8; if (_bit_offset<0) { _bit_offset+=8; --_current_byte; } } difference_type bit_distance_to(const bit_range& b) const { return (b.current_byte() - current_byte())*8 + b.bit_offset()-bit_offset(); } byte_t* current_byte() const { return _current_byte; } int bit_offset() const { return _bit_offset; } }; /// \defgroup ColorBaseModelNonAlignedPixel bit_aligned_pixel_reference /// \ingroup ColorBaseModel /// \brief A heterogeneous color base representing pixel that may not be byte aligned, i.e. it may correspond to a bit range that does not start/end at a byte boundary. Models ColorBaseConcept. /// /// \defgroup PixelModelNonAlignedPixel bit_aligned_pixel_reference /// \ingroup PixelModel /// \brief A heterogeneous pixel reference used to represent non-byte-aligned pixels. Models PixelConcept /// /// Example: /// \code /// unsigned char data=0; /// /// // A mutable reference to a 6-bit BGR pixel in "123" format (1 bit for red, 2 bits for green, 3 bits for blue) /// using rgb123_ref_t = bit_aligned_pixel_reference<unsigned char, mp11::mp_list_c<int,1,2,3>, rgb_layout_t, true> const; /// /// // create the pixel reference at bit offset 2 /// // (i.e. red = [2], green = [3,4], blue = [5,6,7] bits) /// rgb123_ref_t ref(&data, 2); /// get_color(ref, red_t()) = 1; /// assert(data == 0x04); /// get_color(ref, green_t()) = 3; /// assert(data == 0x1C); /// get_color(ref, blue_t()) = 7; /// assert(data == 0xFC); /// \endcode /// /// \ingroup ColorBaseModelNonAlignedPixel PixelModelNonAlignedPixel PixelBasedModel /// \brief Heterogeneous pixel reference corresponding to non-byte-aligned bit range. Models ColorBaseConcept, PixelConcept, PixelBasedConcept /// /// \tparam BitField /// \tparam ChannelBitSizes Boost.MP11-compatible list of integral types defining the number of bits for each channel. For example, for 565RGB, mp_list_c<int,5,6,5> /// \tparam Layout /// \tparam IsMutable template <typename BitField, typename ChannelBitSizes, typename Layout, bool IsMutable> struct bit_aligned_pixel_reference { static constexpr int bit_size = mp11::mp_fold < ChannelBitSizes, std::integral_constant<int, 0>, mp11::mp_plus >::value; using bit_range_t = boost::gil::bit_range<bit_size,IsMutable>; using bitfield_t = BitField; using data_ptr_t = mp11::mp_if_c<IsMutable, unsigned char*, const unsigned char*>; using layout_t = Layout; using value_type = typename packed_pixel_type<bitfield_t,ChannelBitSizes,Layout>::type; using reference = const bit_aligned_pixel_reference<BitField, ChannelBitSizes, Layout, IsMutable>; using const_reference = bit_aligned_pixel_reference<BitField,ChannelBitSizes,Layout,false> const; static constexpr bool is_mutable = IsMutable; bit_aligned_pixel_reference(){} bit_aligned_pixel_reference(data_ptr_t data_ptr, int bit_offset) : _bit_range(data_ptr, bit_offset) {} explicit bit_aligned_pixel_reference(const bit_range_t& bit_range) : _bit_range(bit_range) {} template <bool IsMutable2> bit_aligned_pixel_reference(const bit_aligned_pixel_reference<BitField,ChannelBitSizes,Layout,IsMutable2>& p) : _bit_range(p._bit_range) {} // Grayscale references can be constructed from the channel reference explicit bit_aligned_pixel_reference(typename kth_element_type<bit_aligned_pixel_reference,0>::type const channel0) : _bit_range(static_cast<data_ptr_t>(&channel0), channel0.first_bit()) { static_assert(num_channels<bit_aligned_pixel_reference>::value == 1, ""); } // Construct from another compatible pixel type bit_aligned_pixel_reference(bit_aligned_pixel_reference const& p) : _bit_range(p._bit_range) {} // TODO: Why p by non-const reference? template <typename BF, typename CR> bit_aligned_pixel_reference(packed_pixel<BF, CR, Layout>& p) : _bit_range(static_cast<data_ptr_t>(&gil::at_c<0>(p)), gil::at_c<0>(p).first_bit()) { check_compatible<packed_pixel<BF, CR, Layout>>(); } auto operator=(bit_aligned_pixel_reference const& p) const -> bit_aligned_pixel_reference const& { static_copy(p, *this); return *this; } template <typename P> auto operator=(P const& p) const -> bit_aligned_pixel_reference const& { assign(p, is_pixel<P>()); return *this; } template <typename P> bool operator==(P const& p) const { return equal(p, is_pixel<P>()); } template <typename P> bool operator!=(P const& p) const { return !(*this==p); } auto operator->() const -> bit_aligned_pixel_reference const* { return this; } bit_range_t const& bit_range() const { return _bit_range; } private: mutable bit_range_t _bit_range; template <typename B, typename C, typename L, bool M> friend struct bit_aligned_pixel_reference; template <typename Pixel> static void check_compatible() { gil_function_requires<PixelsCompatibleConcept<Pixel,bit_aligned_pixel_reference> >(); } template <typename Pixel> void assign(Pixel const& p, std::true_type) const { 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); } private: 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) const { 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; } }; ///////////////////////////// // ColorBasedConcept ///////////////////////////// template <typename BitField, typename ChannelBitSizes, typename L, bool IsMutable, int K> struct kth_element_type < bit_aligned_pixel_reference<BitField, ChannelBitSizes, L, IsMutable>, K > { using type = packed_dynamic_channel_reference < BitField, mp11::mp_at_c<ChannelBitSizes, K>::value, IsMutable > const; }; template <typename B, typename C, typename L, bool M, int K> struct kth_element_reference_type<bit_aligned_pixel_reference<B,C,L,M>, K> : public kth_element_type<bit_aligned_pixel_reference<B,C,L,M>, K> {}; template <typename B, typename C, typename L, bool M, int K> struct kth_element_const_reference_type<bit_aligned_pixel_reference<B,C,L,M>, K> : public kth_element_type<bit_aligned_pixel_reference<B,C,L,M>, K> {}; namespace detail { // returns sum of IntegralVector[0] ... IntegralVector[K-1] template <typename IntegralVector, int K> struct sum_k : mp11::mp_plus < sum_k<IntegralVector, K - 1>, typename mp11::mp_at_c<IntegralVector, K - 1>::type > {}; template <typename IntegralVector> struct sum_k<IntegralVector, 0> : std::integral_constant<int, 0> {}; } // namespace detail // at_c required by MutableColorBaseConcept template <int K, typename BitField, typename ChannelBitSizes, typename L, bool IsMutable> inline auto at_c(const bit_aligned_pixel_reference<BitField, ChannelBitSizes, L, IsMutable>& p) -> typename kth_element_reference_type<bit_aligned_pixel_reference<BitField, ChannelBitSizes, L, IsMutable>, K>::type { using pixel_t = bit_aligned_pixel_reference<BitField, ChannelBitSizes, L, IsMutable>; using channel_t = typename kth_element_reference_type<pixel_t, K>::type; using bit_range_t = typename pixel_t::bit_range_t; bit_range_t bit_range(p.bit_range()); bit_range.bit_advance(detail::sum_k<ChannelBitSizes, K>::value); return channel_t(bit_range.current_byte(), bit_range.bit_offset()); } ///////////////////////////// // PixelConcept ///////////////////////////// /// Metafunction predicate that flags bit_aligned_pixel_reference as a model of PixelConcept. Required by PixelConcept template <typename B, typename C, typename L, bool M> struct is_pixel<bit_aligned_pixel_reference<B, C, L, M> > : std::true_type {}; ///////////////////////////// // PixelBasedConcept ///////////////////////////// template <typename B, typename C, typename L, bool M> struct color_space_type<bit_aligned_pixel_reference<B, C, L, M>> { using type = typename L::color_space_t; }; template <typename B, typename C, typename L, bool M> struct channel_mapping_type<bit_aligned_pixel_reference<B, C, L, M>> { using type = typename L::channel_mapping_t; }; template <typename B, typename C, typename L, bool M> struct is_planar<bit_aligned_pixel_reference<B, C, L, M>> : std::false_type {}; ///////////////////////////// // pixel_reference_type ///////////////////////////// // Constructs a homogeneous bit_aligned_pixel_reference given a channel reference template <typename BitField, int NumBits, typename Layout> struct pixel_reference_type < packed_dynamic_channel_reference<BitField, NumBits, false> const, Layout, false, false > { private: using channel_bit_sizes_t = mp11::mp_repeat < mp11::mp_list<std::integral_constant<unsigned, NumBits>>, mp11::mp_size<typename Layout::color_space_t> >; public: using type = bit_aligned_pixel_reference<BitField, channel_bit_sizes_t, Layout, false>; }; // Same but for the mutable case. We cannot combine the mutable // and read-only cases because this triggers ambiguity template <typename BitField, int NumBits, typename Layout> struct pixel_reference_type < packed_dynamic_channel_reference<BitField, NumBits, true> const, Layout, false, true > { private: using channel_bit_sizes_t = mp11::mp_repeat < mp11::mp_list<std::integral_constant<unsigned, NumBits>>, mp11::mp_size<typename Layout::color_space_t> >; public: using type = bit_aligned_pixel_reference<BitField, channel_bit_sizes_t, Layout, true>; }; } } // namespace boost::gil namespace std { // We are forced to define swap inside std namespace because on some platforms (Visual Studio 8) STL calls swap qualified. // swap with 'left bias': // - swap between proxy and anything // - swap between value type and proxy // - swap between proxy and proxy // Having three overloads allows us to swap between different (but compatible) models of PixelConcept template <typename B, typename C, typename L, typename R> inline void swap(const boost::gil::bit_aligned_pixel_reference<B,C,L,true> x, R& y) { boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y); } template <typename B, typename C, typename L> inline void swap(typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type& x, const boost::gil::bit_aligned_pixel_reference<B,C,L,true> y) { boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y); } template <typename B, typename C, typename L> inline void swap(const boost::gil::bit_aligned_pixel_reference<B,C,L,true> x, const boost::gil::bit_aligned_pixel_reference<B,C,L,true> y) { boost::gil::swap_proxy<typename boost::gil::bit_aligned_pixel_reference<B,C,L,true>::value_type>(x,y); } } // namespace std #endif
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