ceph/src/boost/libs/geometry/doc/src/examples/algorithms/for_each_point.cpp

   1 // Boost.Geometry (aka GGL, Generic Geometry Library)
   2 // QuickBook Example
   3
   4 // Copyright (c) 2011-2012 Barend Gehrels, Amsterdam, the Netherlands.
   5
   6 // Use, modification and distribution is subject to the Boost Software License,
   7 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   8 // http://www.boost.org/LICENSE_1_0.txt)
   9
  10 //[for_each_point
  11 //` Convenient usage of for_each_point, rounding all points of a geometry
  12
  13 #include <iostream>
  14
  15 #include <boost/geometry.hpp>
  16 #include <boost/geometry/geometries/point_xy.hpp>
  17 #include <boost/geometry/geometries/polygon.hpp>
  18
  19
  20
  21 template <typename Point>
  22 class round_coordinates
  23 {
  24 private :
  25     typedef typename boost::geometry::coordinate_type<Point>::type coordinate_type;
  26     coordinate_type factor;
  27
  28     inline coordinate_type round(coordinate_type value)
  29     {
  30         return floor(0.5 + (value / factor)) * factor;
  31     }
  32
  33 public :
  34     round_coordinates(coordinate_type f)
  35         : factor(f)
  36     {}
  37
  38     inline void operator()(Point& p)
  39     {
  40         using boost::geometry::get;
  41         using boost::geometry::set;
  42         set<0>(p, round(get<0>(p)));
  43         set<1>(p, round(get<1>(p)));
  44     }
  45 };
  46
  47
  48 int main()
  49 {
  50     typedef boost::geometry::model::d2::point_xy<double> point;
  51     boost::geometry::model::polygon<point> poly;
  52     boost::geometry::read_wkt("POLYGON((0 0,1.123 9.987,8.876 2.234,0 0),(3.345 4.456,7.654 8.765,9.123 5.432,3.345 4.456))", poly);
  53     boost::geometry::for_each_point(poly, round_coordinates<point>(0.1));
  54     std::cout << "Rounded: " << boost::geometry::wkt(poly) << std::endl;
  55     return 0;
  56 }
  57
  58 //]
  59
  60
  61 //[for_each_point_output
  62 /*`
  63 Output:
  64 [pre
  65  Rounded: POLYGON((0 0,1.1 10,8.9 2.2,0 0),(3.3 4.5,7.7 8.8,9.1 5.4,3.3 4.5))
  66 ]
  67 */
  68 //]