Port TuttleOFX extension : shrink

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/shrink.hpp>
 
 #endif

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

@@ -0,0 +1,54 @@
+// 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 BOOST_GIL_EXTENSION_TOOLBOX_METAFUNCTIONS_SHRINK_HPP
+#define BOOST_GIL_EXTENSION_TOOLBOX_METAFUNCTIONS_SHRINK_HPP
+
+#include <boost/gil.hpp>
+
+namespace boost { namespace gil {
+
+/// \brief Assigns a smaller subimage view of the view given as first parameter to the
+/// destination/resultant view given as second parameter to the overloaded '()' operator.
+/// The dimensions of the smaller view are specified by struct constructor parameters.
+template <typename View>
+struct shrink
+{
+    double left;
+    double top;
+    double right;
+    double bottom;
+
+    shrink(double left_param = 5, double top_param = 5, double right_param = 5,
+        double bottom_param = 5)
+        : left(left_param)
+        , top(top_param)
+        , right(right_param)
+        , bottom(bottom_param)
+    {
+    }
+
+    void operator()(View& view, View& dstView)
+    {
+        double const view_width = static_cast<double>(view.width());
+        double const view_height = static_cast<double>(view.height());
+        if (left < 1.0)
+            left *= view_width;
+        if (right < 1.0)
+            right *= view_width;
+        if (top < 1.0)
+            top *= view_height;
+        if (bottom < 1.0)
+            bottom *= view_height;
+
+        double const width = view_width - left - right;
+        double const height = view_height - top - bottom;
+        dstView = boost::gil::subimage_view(view, static_cast<std::ptrdiff_t>(left),
+            static_cast<std::ptrdiff_t>(top), static_cast<std::ptrdiff_t>(width),
+            static_cast<std::ptrdiff_t>(height));
+    }
+}; // shrink
+}} // namespace boost::gil
+
+#endif

test/extension/toolbox/CMakeLists.txt

@@ -24,6 +24,7 @@ foreach(_name
   is_bit_aligned
   is_homogeneous
   pixel_bit_size
+  shrink
   subchroma_image)
   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 shrink.cpp ;
 
 # TODO: Add subchroma_image.cpp after fixing run-time failure,
 #      for details see https://github.com/boostorg/gil/pull/164

test/extension/toolbox/shrink.cpp

@@ -0,0 +1,31 @@
+//
+// Copyright 2021 Prathamesh Tagore <prathameshtagore@gmail.com>
+//
+// Use, modification and distribution are subject to 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)
+//
+
+// Reference for test case was taken from
+// https://github.com/tuttleofx/TuttleOFX/blob/develop/libraries/boostHack/boost/gil/extension/toolbox/shrink.tests.cpp
+
+#include <boost/gil/extension/toolbox/metafunctions.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+namespace gil = boost::gil;
+
+int main()
+{
+    gil::rgb8_image_t original_img(20, 20), expected_img(12, 8);
+    gil::rgb8_view_t original_img_view = gil::view(original_img), obtained_img_view;
+
+    gil::fill_pixels(original_img_view, gil::rgb8_pixel_t(255, 255, 255));
+    gil::fill_pixels(gil::view(expected_img), gil::rgb8_pixel_t(255, 255, 255));
+
+    gil::shrink<gil::rgb8_view_t> shrink(0.20, 0.30, 0.20, 0.30);
+    shrink(original_img_view, obtained_img_view);
+
+    BOOST_TEST(gil::equal_pixels(obtained_img_view, gil::view(expected_img)));
+
+    return boost::report_errors();
+}