Imported Upstream version 1.72.0

[platform/upstream/boost.git] / boost / gil / color_convert.hpp

diff --git a/boost/gil/color_convert.hpp b/boost/gil/color_convert.hpp
index 815bc48..3ebcd0c 100644 (file)
--- a/boost/gil/color_convert.hpp
+++ b/boost/gil/color_convert.hpp
@@ -20,6 +20,7 @@
 
 #include <algorithm>
 #include <functional>
+#include <type_traits>
 
 namespace boost { namespace gil {
 
@@ -211,20 +212,27 @@ struct default_color_converter_impl<cmyk_t,gray_t> {
 };
 
 namespace detail {
+
 template <typename Pixel>
-typename channel_type<Pixel>::type alpha_or_max_impl(const Pixel& p, mpl::true_) {
+auto alpha_or_max_impl(Pixel const& p, std::true_type) -> typename channel_type<Pixel>::type
+{
     return get_color(p,alpha_t());
 }
 template <typename Pixel>
-typename channel_type<Pixel>::type alpha_or_max_impl(const Pixel&  , mpl::false_) {
+auto alpha_or_max_impl(Pixel const&, std::false_type) -> typename channel_type<Pixel>::type
+{
     return channel_traits<typename channel_type<Pixel>::type>::max_value();
 }
+
 } // namespace detail
 
 // Returns max_value if the pixel has no alpha channel. Otherwise returns the alpha.
 template <typename Pixel>
-typename channel_type<Pixel>::type alpha_or_max(const Pixel& p) {
-    return detail::alpha_or_max_impl(p, mpl::contains<typename color_space_type<Pixel>::type,alpha_t>());
+auto alpha_or_max(Pixel const& p) -> typename channel_type<Pixel>::type
+{
+    return detail::alpha_or_max_impl(
+        p,
+        mp11::mp_contains<typename color_space_type<Pixel>::type, alpha_t>());
 }