generic geometry transform algorithm

include/mapnik/geometry_transform.hpp

@@ -0,0 +1,83 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2015 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_GEOMETRY_TRANSFORM_HPP
+#define MAPNIK_GEOMETRY_TRANSFORM_HPP
+
+#include <mapnik/geometry.hpp>
+#include <mapnik/geometry_adapters.hpp>
+#include <boost/geometry/algorithms/transform.hpp>
+
+namespace mapnik { namespace geometry { namespace detail {
+
+template <typename Transformer>
+struct geometry_transform
+{
+    geometry_transform(Transformer const& transformer)
+        : transformer_(transformer) {}
+
+    using result_type = geometry;
+
+    geometry operator() (geometry_empty const& empty) const
+    {
+        return empty;
+    }
+
+    geometry operator() (geometry_collection const& collection) const
+    {
+        geometry_collection collection_out;
+        for (auto const& geom :  collection)
+        {
+            collection_out.push_back(std::move((*this)(geom)));
+        }
+        return collection_out;
+    }
+
+    geometry operator() (geometry const& geom) const
+    {
+        return mapnik::util::apply_visitor(*this, geom);
+    }
+
+    template <typename T>
+    geometry operator() (T const& geom) const
+    {
+        using geometry_type = T;
+        geometry_type geom_transformed;
+        if (!boost::geometry::transform(geom, geom_transformed, transformer_))
+        {
+            throw std::runtime_error("Can't transformm geometry");
+        }
+        return geom_transformed;
+    }
+    Transformer const& transformer_;
+};
+} // ns detail
+
+template <typename T0, typename T1>
+geometry transform(T0 const& geom, T1 const& transformer)
+{
+    return detail::geometry_transform<T1>(transformer)(geom);
+}
+
+}}
+
+#endif // MAPNIK_GEOMETRY_TRANSFORM_HPP