Add image constructor from compatible view (#520)

* Use pixels_are_compatible instead of std::is_convertible

.gitignore

@@ -15,6 +15,7 @@ doc/warnings.txt
 /.vs
 .vscode
 *.code-workspace
+out
 
 # Clang/LLVM
 /.clang-format

include/boost/gil/image.hpp

@@ -110,6 +110,16 @@ class image
        allocate_and_copy(img.dimensions(),img._view);
     }
 
+    template <typename Loc,
+              typename std::enable_if<pixels_are_compatible<typename Loc::value_type, Pixel>::value, int>::type = 0>
+    image(const image_view<Loc>& view,
+          std::size_t alignment = 0,
+          const Alloc alloc_in = Alloc()) : _memory(nullptr), _align_in_bytes(alignment), _alloc(alloc_in)
+                                          , _allocated_bytes( 0 )
+    {
+       allocate_and_copy(view.dimensions(),view);
+    }
+
     // TODO Optimization: use noexcept (requires _view to be nothrow copy constructible)
     image(image&& img) :
       _view(img._view),

test/core/image/image.cpp

@@ -72,6 +72,31 @@ struct test_constructor_from_other_image
     }
 };
 
+struct test_constructor_from_view
+{
+    template <typename Image>
+    void operator()(Image const&)
+    {
+        using image_t = Image;
+        gil::point_t const dimensions{ 256, 128 };
+        using pixel_t = typename image_t::view_t::value_type;
+        pixel_t const rnd_pixel = fixture::pixel_generator<pixel_t>::random();
+        {
+            //constructor interleaved from planar
+            gil::image<pixel_t, true> image1(dimensions, rnd_pixel);
+            auto v1 = gil::transposed_view(gil::const_view(image1));
+            image_t image2(gil::transposed_view(v1));
+            BOOST_TEST_EQ(image2.dimensions(), dimensions);
+            auto v2 = gil::const_view(image2);
+            BOOST_TEST_ALL_EQ(v1.begin(), v1.end(), v2.begin(), v2.end());
+        }
+    }
+    static void run()
+    {
+        boost::mp11::mp_for_each<fixture::rgb_interleaved_image_types>(test_constructor_from_view{});
+    }
+};
+
 struct test_move_constructor
 {
     template <typename Image>