...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Returns one or more points interpolated along a LineString.
template<typename Geometry, typename Distance, typename Pointlike> void line_interpolate(Geometry const & geometry, Distance const & max_distance, Pointlike & pointlike)
Type |
Concept |
Name |
Description |
---|---|---|---|
Geometry const & |
Any type fulfilling a LineString concept |
geometry |
Input geometry |
Distance const & |
A numerical distance measure |
max_distance |
Distance threshold (in units depending on coordinate system) representing the spacing between the points |
Pointlike & |
Any type fulfilling Point or Multipoint concept |
pointlike |
Output: either a Point (exactly one point will be constructed) or a MultiPoint (depending on the max_distance one or more points will be constructed) |
Either
#include <boost/geometry.hpp>
Or
#include <boost/geometry/algorithms/line_interpolate.hpp>
The function line_interpolate_point is not defined by OGC.
Note | |
---|---|
PostGIS contains an algorithm ST_LineInterpolatePoints with similar functionality. See the PostGIS documentation. |
The algorithm iterates among segments of the linestring and computes interpolation points if needed.
Shows how to interpolate points on a linestring
#include <iostream> #include <boost/geometry.hpp> #include <boost/geometry/geometries/point_xy.hpp> using namespace boost::geometry; int main() { using point_type = boost::geometry::model::d2::point_xy<double>; using segment_type = model::segment<point_type>; using linestring_type = model::linestring<point_type>; using multipoint_type = model::multi_point<point_type>; segment_type const s { {0, 0}, {1, 1} }; linestring_type const l { {0, 0}, {1, 0}, {1, 1}, {0, 1}, {0, 2} }; point_type p; multipoint_type mp; std::cout << "point interpolation" << std::endl; line_interpolate(s, std::sqrt(2)/4, p); std::cout << "on segment : " << wkt(p) << std::endl; line_interpolate(l, 1.4, p); std::cout << "on linestring : " << wkt(p) << std::endl << std::endl; std::cout << "multipoint interpolation" << std::endl; line_interpolate(s, std::sqrt(2)/4, mp); std::cout << "on segment : " << wkt(mp) << std::endl; mp=multipoint_type(); line_interpolate(l, 1.4, mp); std::cout << "on linestring : " << wkt(mp) << std::endl; return 0; }
Output:
point interpolation on segment : POINT(0.25 0.25) on linestring : POINT(1 0.4) multipoint interpolation on segment : MULTIPOINT((0.25 0.25),(0.5 0.5),(0.75 0.75),(1 1)) on linestring : MULTIPOINT((1 0.4),(0.2 1))