boost/gil/extension/toolbox/metafunctions/channel_type.hpp

   1 //
   2 // Copyright 2012 Christian Henning, Andreas Pokorny, Lubomir Bourdev
   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_EXTENSION_TOOLBOX_METAFUNCTIONS_CHANNEL_TYPE_HPP
   9 #define BOOST_GIL_EXTENSION_TOOLBOX_METAFUNCTIONS_CHANNEL_TYPE_HPP
  10
  11 #include <boost/gil/extension/toolbox/dynamic_images.hpp>
  12 #include <boost/gil/extension/toolbox/metafunctions/get_num_bits.hpp>
  13 #include <boost/gil/extension/toolbox/metafunctions/is_homogeneous.hpp>
  14
  15 #include <boost/gil/bit_aligned_pixel_reference.hpp>
  16 #include <boost/gil/channel.hpp>
  17 #include <boost/gil/detail/mp11.hpp>
  18
  19 #include <boost/utility/enable_if.hpp> // boost::lazy_enable_if
  20
  21 namespace boost{ namespace gil {
  22
  23 /// channel_type metafunction
  24 /// \brief Generates the channel type for
  25
  26 template <typename B, typename C, typename L, bool M>
  27 struct gen_chan_ref
  28 {
  29     using type = packed_dynamic_channel_reference
  30         <
  31             B,
  32             mp11::mp_at_c<C, 0>::value,
  33             M
  34         >;
  35 };
  36
  37 //! This implementation works for bit_algined_pixel_reference
  38 //! with a homogeneous channel layout.
  39 //! The result type will be a packed_dynamic_channel_reference, since the
  40 //! offset info will be missing.
  41
  42 // bit_aligned_pixel_reference
  43 template <typename B, typename C, typename L, bool M>
  44 struct channel_type< bit_aligned_pixel_reference<B,C,L,M> >
  45     : lazy_enable_if< is_homogeneous< bit_aligned_pixel_reference< B, C, L, M > >
  46                     , gen_chan_ref< B, C, L, M >
  47                     > {};
  48
  49 template <typename B, typename C, typename L, bool M>
  50 struct channel_type<const bit_aligned_pixel_reference<B,C,L,M> >
  51     : lazy_enable_if< is_homogeneous< bit_aligned_pixel_reference< B, C, L, M > >
  52                     , gen_chan_ref< B, C, L, M >
  53                     > {};
  54
  55 template <typename B, typename C, typename L>
  56 struct gen_chan_ref_p
  57 {
  58     using type = packed_dynamic_channel_reference
  59         <
  60             B,
  61             get_num_bits<mp11::mp_at_c<C, 0>>::value,
  62             true
  63         >;
  64 };
  65
  66 // packed_pixel
  67 template < typename BitField
  68          , typename ChannelRefs
  69          , typename Layout
  70          >
  71 struct channel_type< packed_pixel< BitField
  72                                  , ChannelRefs
  73                                  , Layout
  74                                  >
  75                    > : lazy_enable_if< is_homogeneous< packed_pixel< BitField
  76                                                                    , ChannelRefs
  77                                                                    , Layout
  78                                                                    >
  79                                                      >
  80                                      , gen_chan_ref_p< BitField
  81                                                      , ChannelRefs
  82                                                      , Layout
  83                                                      >
  84                                      > {};
  85
  86 template <typename B, typename C, typename L>
  87 struct channel_type< const packed_pixel< B, C, L > >
  88     : lazy_enable_if< is_homogeneous<packed_pixel< B, C, L > >
  89                     , gen_chan_ref_p< B, C, L >
  90                     >
  91 {};
  92
  93 template<>
  94 struct channel_type< any_image_pixel_t >
  95 {
  96     using type = any_image_channel_t;
  97 };
  98
  99 } // namespace gil
 100 } // namespace boost
 101
 102 #endif