libs/gil/example/interleaved_ref.hpp

   1 //
   2 // Copyright 2005-2007 Adobe Systems Incorporated
   3 //
   4 // Distributed under the Boost Software License, Version 1.0
   5 // See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt
   7 //
   8 #ifndef BOOST_GIL_EXAMPLE_INTERLEAVED_REF_HPP
   9 #define BOOST_GIL_EXAMPLE_INTERLEAVED_REF_HPP
  10
  11 #include <boost/gil.hpp>
  12 #include <boost/gil/extension/dynamic_image/dynamic_image_all.hpp>
  13
  14 #include <type_traits>
  15
  16 // Example on how to create a new model of a pixel reference
  17
  18 namespace boost { namespace gil {
  19
  20 // A model of an interleaved pixel reference. Holds a pointer to the first channel
  21 // MODELS:
  22 //    MutableHomogeneousPixelConcept
  23 //       MutableHomogeneousColorBaseConcept
  24 //           MutableColorBaseConcept
  25 //           HomogeneousColorBaseConcept
  26 //               ColorBaseConcept
  27 //    HomogeneousPixelBasedConcept
  28 //       PixelBasedConcept
  29 //
  30 // For planar reference proxies to work properly, all of their methods must be const-qualified
  31 // and their iterator's reference type must be const-qualified.
  32 // Mutability of the reference proxy is part of its type (in this case, depends on the mutability of ChannelReference)
  33
  34 /// \tparam ChannelReference - Models ChannelConcept.
  35 ///         A channel reference, unsigned char& or const unsigned char&
  36 /// \tparam Layout - A layout (includes the color space and channel ordering)
  37 template <typename ChannelReference, typename Layout>
  38 struct interleaved_ref
  39 {
  40 private:
  41     using channel_t = typename channel_traits<ChannelReference>::value_type;
  42     using channel_pointer_t = typename channel_traits<ChannelReference>::pointer;
  43     using channel_reference_t = typename channel_traits<ChannelReference>::reference;
  44     using channel_const_reference_t = typename channel_traits<ChannelReference>::const_reference;
  45
  46 public:
  47     using layout_t = Layout; // Required by ColorBaseConcept
  48
  49     // Copy construction from a compatible type. The copy constructor of references is shallow. The channels themselves are not copied.
  50     interleaved_ref(const interleaved_ref& p) : _channels(p._channels) {}
  51     template <typename P> interleaved_ref(const P& p) : _channels(p._channels) { check_compatible<P>(); }
  52
  53     template <typename P> bool operator==(const P& p)    const { check_compatible<P>(); return static_equal(*this,p); }
  54     template <typename P> bool operator!=(const P& p)    const { return !(*this==p); }
  55
  56 // Required by MutableColorBaseConcept
  57
  58     // Assignment from a compatible type
  59     const interleaved_ref&  operator=(const interleaved_ref& p)  const { static_copy(p,*this); return *this; }
  60     template <typename P> const interleaved_ref& operator=(const P& p) const { check_compatible<P>(); static_copy(p,*this); return *this; }
  61
  62 // Required by PixelConcept
  63     using value_type = pixel<channel_t, layout_t>;
  64     using reference = interleaved_ref;
  65     using const_reference = interleaved_ref<channel_const_reference_t, layout_t>;
  66     static const bool is_mutable = channel_traits<ChannelReference>::is_mutable;
  67
  68 // Required by HomogeneousPixelConcept
  69     ChannelReference                   operator[](std::size_t i) const { return _channels[i]; }
  70
  71 // Custom constructor (not part of any concept)
  72     explicit interleaved_ref(channel_pointer_t channels) : _channels(channels) {}
  73 // This is needed for the reference proxy to work properly
  74     const interleaved_ref*             operator->()              const { return this; }
  75 private:
  76     channel_pointer_t _channels;
  77
  78     template <typename Pixel> static void check_compatible() { gil_function_requires<PixelsCompatibleConcept<Pixel,interleaved_ref>>(); }
  79 };
  80
  81 // Required by ColorBaseConcept
  82 template <typename ChannelReference, typename Layout, int K>
  83 struct kth_element_type<interleaved_ref<ChannelReference, Layout>, K>
  84 {
  85     using type = ChannelReference;
  86 };
  87
  88 template <typename ChannelReference, typename Layout, int K>
  89 struct kth_element_reference_type<interleaved_ref<ChannelReference, Layout>, K>
  90 {
  91     using type = ChannelReference;
  92 };
  93
  94 template <typename ChannelReference, typename Layout, int K>
  95 struct kth_element_const_reference_type<interleaved_ref<ChannelReference, Layout>, K>
  96 {
  97     using type = ChannelReference;
  98     // XXX: using type = typename channel_traits<ChannelReference>::const_reference;
  99 };
 100
 101 // Required by ColorBaseConcept
 102 template <int K, typename ChannelReference, typename Layout>
 103 typename element_reference_type<interleaved_ref<ChannelReference,Layout>>::type
 104 at_c(const interleaved_ref<ChannelReference,Layout>& p) { return p[K]; };
 105
 106 // Required by HomogeneousColorBaseConcept
 107 template <typename ChannelReference, typename Layout>
 108 typename element_reference_type<interleaved_ref<ChannelReference,Layout>>::type
 109 dynamic_at_c(const interleaved_ref<ChannelReference,Layout>& p, std::size_t n) { return p[n]; };
 110
 111 namespace detail {
 112     struct swap_fn_t {
 113         template <typename T> void operator()(T& x, T& y) const {
 114             using std::swap;
 115             swap(x,y);
 116         }
 117     };
 118 }
 119
 120 // Required by MutableColorBaseConcept. The default std::swap does not do the right thing for proxy references - it swaps the references, not the values
 121 template <typename ChannelReference, typename Layout>
 122 void swap(const interleaved_ref<ChannelReference,Layout>& x, const interleaved_ref<ChannelReference,Layout>& y) {
 123     static_for_each(x,y,detail::swap_fn_t());
 124 };
 125
 126 // Required by PixelConcept
 127 template <typename ChannelReference, typename Layout>
 128 struct is_pixel<interleaved_ref<ChannelReference,Layout>> : public std::true_type {};
 129
 130
 131 // Required by PixelBasedConcept
 132 template <typename ChannelReference, typename Layout>
 133 struct color_space_type<interleaved_ref<ChannelReference, Layout>>
 134 {
 135     using type = typename Layout::color_space_t;
 136 };
 137
 138 // Required by PixelBasedConcept
 139 template <typename ChannelReference, typename Layout>
 140 struct channel_mapping_type<interleaved_ref<ChannelReference, Layout>>
 141 {
 142     using type = typename Layout::channel_mapping_t;
 143 };
 144
 145 // Required by PixelBasedConcept
 146 template <typename ChannelReference, typename Layout>
 147 struct is_planar<interleaved_ref<ChannelReference,Layout>> : std::false_type {};
 148
 149 // Required by HomogeneousPixelBasedConcept
 150 template <typename ChannelReference, typename Layout>
 151 struct channel_type<interleaved_ref<ChannelReference, Layout>>
 152 {
 153     using type = typename channel_traits<ChannelReference>::value_type;
 154 };
 155
 156 } }  // namespace boost::gil
 157
 158 #endif