Port TuttleOFX extension : aligned

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

@@ -16,5 +16,6 @@
 #include <boost/gil/extension/toolbox/metafunctions/is_homogeneous.hpp>
 #include <boost/gil/extension/toolbox/metafunctions/is_similar.hpp>
 #include <boost/gil/extension/toolbox/metafunctions/pixel_bit_size.hpp>
+#include <boost/gil/extension/toolbox/metafunctions/aligned.hpp>
 
 #endif

include/boost/gil/extension/toolbox/metafunctions/aligned.hpp

@@ -0,0 +1,70 @@
+// Copyright Tom Brinkman 2008. Distributed under the Boost
+// Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef _aligned_hpp_
+#define _aligned_hpp_
+
+#include <boost/gil.hpp>
+
+namespace boost { namespace gil {
+
+/// \brief Aligns the image view passed through struct constructor in a specific direction
+/// inside the image view passed through the overloaded '()' operator. The direction of 
+/// alignment is specified by constructor parameters.
+template <typename view_t>
+struct aligned
+{
+    // Following enum variables will be used for specifying alignment of view passed through
+    // constructor with respect to the view passed through overloaded '()' operator.
+    enum
+    {
+        left = (0x1 << 0),
+        center = (0x1 << 1),
+        right = (0x1 << 2),
+        top = (0x1 << 3),
+        middle = (0x1 << 5),
+        bottom = (0x1 << 7),
+    };
+
+    view_t& v2;
+    int align;
+    aligned(view_t v2, int align = center | middle)
+        : v2(v2)
+        , align(align)
+    {
+    }
+
+    void operator()(view_t& view)
+    {
+        using namespace boost::gil;
+
+        std::size_t w = v2.width(), h = v2.height();
+
+        // For ensuring that view passed through '()' operator has dimensions greater than or
+        // equal to the dimensions of view passed through constructor.
+        if (h > view.height() || w > view.width())
+        {
+            throw std::length_error("Image view passed through overloaded '()' operator must have"
+                " dimensions greater than or equal to the dimensions of image view passed through"
+                " struct constructor");
+        }
+
+        std::ptrdiff_t x = 0;
+        if (align & center)
+            x = (view.width() - w) / 2;
+        else if (align & right)
+            x = view.width() - w;
+
+        std::ptrdiff_t y = 0;
+        if (align & middle)
+            y = (view.height() - h) / 2;
+        else if (align & bottom)
+            y = view.height() - h;
+
+        view_t v3 = subimage_view(view, x, y, w, h);
+        copy_pixels(v2, v3);
+    }
+}; // shrink
+}} // namespace boost::gil
+#endif

test/extension/toolbox/CMakeLists.txt

@@ -24,7 +24,8 @@ foreach(_name
   is_bit_aligned
   is_homogeneous
   pixel_bit_size
-  subchroma_image)
+  subchroma_image
+  aligned)
   set(_test t_ext_toolbox_${_name})
   set(_target test_ext_toolbox_${_name})
 

test/extension/toolbox/Jamfile

@@ -27,6 +27,7 @@ run color_convert_lab.cpp ;
 run color_convert_luminance.cpp ;
 run color_convert_xyz.cpp ;
 run indexed_image.cpp ;
+run aligned.cpp ;
 
 # TODO: Add subchroma_image.cpp after fixing run-time failure,
 #      for details see https://github.com/boostorg/gil/pull/164