boost/gil/extension/toolbox/color_spaces/lab.hpp

   1 //
   2 // Copyright 2012 Chung-Lin Wen
   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_COLOR_SPACES_LAB_HPP
   9 #define BOOST_GIL_EXTENSION_TOOLBOX_COLOR_SPACES_LAB_HPP
  10
  11 #include <boost/gil/extension/toolbox/color_spaces/xyz.hpp>
  12
  13 #include <boost/gil/color_convert.hpp>
  14 #include <boost/gil.hpp> // FIXME: Include what you use, not everything, even in extensions!
  15 #include <boost/gil/detail/mp11.hpp>
  16
  17 namespace boost{ namespace gil {
  18
  19 /// \addtogroup ColorNameModel
  20 /// \{
  21 namespace lab_color_space
  22 {
  23 /// \brief Luminance
  24 struct luminance_t {};
  25 /// \brief a Color Component
  26 struct a_color_opponent_t {};
  27 /// \brief b Color Component
  28 struct b_color_opponent_t {};
  29 }
  30 /// \}
  31
  32 /// \ingroup ColorSpaceModel
  33 using lab_t = mp11::mp_list
  34 <
  35     lab_color_space::luminance_t,
  36     lab_color_space::a_color_opponent_t,
  37     lab_color_space::b_color_opponent_t
  38 >;
  39
  40 /// \ingroup LayoutModel
  41 using lab_layout_t = layout<lab_t>;
  42
  43 GIL_DEFINE_ALL_TYPEDEFS(32f, float32_t, lab)
  44
  45 /// \ingroup ColorConvert
  46 /// \brief LAB to XYZ
  47 template <>
  48 struct default_color_converter_impl< lab_t, xyz_t >
  49 {
  50     template <typename P1, typename P2>
  51     void operator()( const P1& src, P2& dst ) const
  52     {
  53         using namespace lab_color_space;
  54         using namespace xyz_color_space;
  55
  56         float32_t p = ((get_color(src, luminance_t()) + 16.f)/116.f);
  57
  58         get_color(dst, y_t()) =
  59                 1.f * powf(p, 3.f);
  60
  61         get_color(dst, x_t()) =
  62                 0.95047f * powf((p +
  63                                  (get_color(src, a_color_opponent_t())/500.f)
  64                                  ), 3.f);
  65         get_color(dst, z_t()) =
  66                 1.08883f * powf((p -
  67                                  (get_color(src, b_color_opponent_t())/200.f)
  68                                  ), 3.f);
  69     }
  70 };
  71
  72 /// \ingroup ColorConvert
  73 /// \brief XYZ to LAB
  74 /// \note I assume \c xyz_t
  75 template <>
  76 struct default_color_converter_impl< xyz_t, lab_t >
  77 {
  78 private:
  79     /// \ref http://www.brucelindbloom.com/index.html?Eqn_XYZ_to_Lab.html
  80     BOOST_FORCEINLINE
  81     float32_t forward_companding(float32_t value) const
  82     {
  83         if (value > 216.f/24389.f)
  84         {
  85             return powf(value, 1.f/3.f);
  86         }
  87         else
  88         {
  89             return ((24389.f/27.f * value + 16.f)/116.f);
  90         }
  91     }
  92
  93 public:
  94     template <typename P1, typename P2>
  95     void operator()( const P1& src, P2& dst ) const
  96     {
  97         using namespace lab_color_space;
  98
  99         float32_t f_y =
 100                 forward_companding(
 101                     channel_convert<float32_t>(
 102                         get_color(src, xyz_color_space::y_t())
 103                         )
 104                     // / 1.f
 105                     );
 106
 107         float32_t f_x =
 108                 forward_companding(
 109                     channel_convert<float32_t>(
 110                         get_color(src, xyz_color_space::x_t())
 111                         )
 112                     * (1.f / 0.95047f)  // if the compiler is smart, it should
 113                                         // precalculate this, no?
 114                     );
 115
 116         float32_t f_z =
 117                 forward_companding(
 118                     channel_convert<float32_t>(
 119                         get_color(src, xyz_color_space::z_t())
 120                         )
 121                     * (1.f / 1.08883f)  // if the compiler is smart, it should
 122                                         // precalculate this, no?
 123                     );
 124
 125         get_color(dst, luminance_t()) =
 126                 116.f * f_y - 16.f;
 127
 128         get_color(dst, a_color_opponent_t()) =
 129                 500.f * (f_x - f_y);
 130
 131         get_color(dst, b_color_opponent_t()) =
 132                 200.f * (f_y - f_z);
 133     }
 134 };
 135
 136
 137 /// \ingroup ColorConvert
 138 /// \brief RGB to LAB
 139 template <>
 140 struct default_color_converter_impl< rgb_t, lab_t >
 141 {
 142     template <typename P1, typename P2>
 143     void operator()( const P1& src, P2& dst ) const
 144     {
 145         using namespace lab_color_space;
 146
 147         xyz32f_pixel_t xyz32f_temp_pixel;
 148         default_color_converter_impl<rgb_t, xyz_t>()(src, xyz32f_temp_pixel);
 149         default_color_converter_impl<xyz_t, lab_t>()(xyz32f_temp_pixel, dst);
 150     }
 151 };
 152
 153 /// \ingroup ColorConvert
 154 /// \brief LAB to RGB
 155 template <>
 156 struct default_color_converter_impl<lab_t,rgb_t>
 157 {
 158     template <typename P1, typename P2>
 159     void operator()( const P1& src, P2& dst) const
 160     {
 161         using namespace lab_color_space;
 162
 163         xyz32f_pixel_t xyz32f_temp_pixel;
 164         default_color_converter_impl<lab_t, xyz_t>()(src, xyz32f_temp_pixel);
 165         default_color_converter_impl<xyz_t, rgb_t>()(xyz32f_temp_pixel, dst);
 166     }
 167 };
 168
 169 } // namespace gil
 170 } // namespace boost
 171
 172 #endif