06_b_transformation_example.cpp

    // Boost.Geometry (aka GGL, Generic Geometry Library)
    // Example: Affine Transformation (translate, scale, rotate)
    //
    // Copyright (c) 2009-2012 Mateusz Loskot, London, UK.
    //
    // Use, modification and distribution is 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)

    #include <ctime> // for std::time
    #include <algorithm>
    #include <fstream>
    #include <iostream>
    #include <limits>
    #include <sstream>

    #include <boost/geometry/geometry.hpp>
    #include <boost/geometry/geometries/point_xy.hpp>
    #include <boost/geometry/geometries/polygon.hpp>
    #include <boost/geometry/algorithms/centroid.hpp>
    #include <boost/geometry/strategies/transform.hpp>
    #include <boost/geometry/strategies/transform/matrix_transformers.hpp>
    #include <boost/geometry/io/wkt/read.hpp>

    #if defined(HAVE_SVG)
    #  include <boost/geometry/io/svg/write_svg.hpp>
    #endif

    #include <boost/random.hpp>
    #include <boost/range.hpp>
    #include <boost/shared_ptr.hpp>

    using namespace boost::geometry;

    struct random_style
    {
        random_style()
            : rng(static_cast<int>(std::time(0))), dist(0, 255), colour(rng, dist)
        {}

        std::string fill(double opacity = 1)
        {
            std::ostringstream oss;
            oss << "fill:rgba(" << colour() << "," << colour() << "," << colour() << "," << opacity << ");";
            return oss.str();
        }

        std::string stroke(int width, double opacity = 1)
        {
            std::ostringstream oss;
            oss << "stroke:rgba(" << colour() << "," << colour() << "," << colour() << "," << opacity << ");";
            oss << "stroke-width:" << width  << ";";
            return oss.str();
        }

        template <typename T>
        std::string text(T x, T y, std::string const& text)
        {
            std::ostringstream oss;
            oss << "<text x=\"" << static_cast<int>(x) - 90 << "\" y=\"" << static_cast<int>(y) << "\" font-family=\"Verdana\">" << text << "</text>";
            return oss.str();
        }

        boost::mt19937 rng;
        boost::uniform_int<> dist;
        boost::variate_generator<boost::mt19937&, boost::uniform_int<> > colour;
    };

    template <typename OutputStream>
    struct svg_output
    {
        svg_output(OutputStream& os, double opacity = 1) : os(os), opacity(opacity)
        {
            os << "<?xml version=\"1.0\" standalone=\"no\"?>\n"
                << "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n"
                << "\"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n"
                << "<svg width=\"100%\" height=\"100%\" version=\"1.1\"\n"
                << "xmlns=\"http://www.w3.org/2000/svg\">" << std::endl;
        }

        ~svg_output()
        {
            os << "</svg>" << std::endl;
        }

        template <typename G>
        void put(G const& g, std::string const& label)
        {
            std::string style_str(style.fill(opacity) + style.stroke(5, opacity));
    #if defined(HAVE_SVG)
            os << boost::geometry::svg(g, style_str) << std::endl;
    #endif
            if (!label.empty())
            {
                typename point_type<G>::type c;
                centroid(g, c);
                os << style.text(static_cast<int>(get<0>(c)), static_cast<int>(get<1>(c)), label);
            }
        }

    private:

        OutputStream& os;
        double opacity;
        random_style style;
    };

    int main()
    {
        using namespace boost::geometry::strategy::transform;

        typedef boost::geometry::model::d2::point_xy<double> point_2d;

        try
        {
            std::string file("06_b_transformation_example.svg");
            std::ofstream ofs(file.c_str());
            svg_output<std::ofstream> svg(ofs, 0.5);

            // G1 - create subject for affine transformations
            model::polygon<point_2d> g1;
            read_wkt("POLYGON((50 250, 400 250, 150 50, 50 250))", g1);
            std::clog << "source box:\t" << boost::geometry::dsv(g1) << std::endl;
            svg.put(g1, "g1");

            // G1 - Translate -> G2
            translate_transformer<double, 2, 2> translate(0, 250);
            model::polygon<point_2d> g2;
            transform(g1, g2, translate);
            std::clog << "translated:\t" << boost::geometry::dsv(g2) << std::endl;
            svg.put(g2, "g2=g1.translate(0,250)");

            // G2 - Scale -> G3
            scale_transformer<double, 2, 2> scale(0.5, 0.5);
            model::polygon<point_2d> g3;
            transform(g2, g3, scale);
            std::clog << "scaled:\t" << boost::geometry::dsv(g3) << std::endl;
            svg.put(g3, "g3=g2.scale(0.5,0.5)");

            // G3 - Combine rotate and translate -> G4
            rotate_transformer<degree, double, 2, 2> rotate(45);

            // Compose matrix for the two transformation
            // Create transformer attached to the transformation matrix
            ublas_transformer<double, 2, 2>
                    combined(boost::numeric::ublas::prod(rotate.matrix(), translate.matrix()));
                    //combined(rotate.matrix());

            // Apply transformation to subject geometry point-by-point
            model::polygon<point_2d> g4;
            transform(g3, g4, combined);

            std::clog << "rotated & translated:\t" << boost::geometry::dsv(g4) << std::endl;
            svg.put(g4, "g4 = g3.(rotate(45) * translate(0,250))");

            std::clog << "Saved SVG file:\t" << file << std::endl;
        }
        catch (std::exception const& e)
        {
            std::cerr << e.what() << std::endl;
        }
        catch (...)
        {
            std::cerr << "unknown error" << std::endl;
        }
        return 0;
    }

April 2, 2011 | Copyright © 2007-2011 Barend Gehrels, Amsterdam, the Netherlands Copyright © 2008-2011 Bruno Lalande, Paris, France Copyright © 2009-2010 Mateusz Loskot, London, UK