src/algorithm/distance/DistanceToPoint.cpp

   1 /**********************************************************************
   2  *
   3  * GEOS - Geometry Engine Open Source
   4  * http://geos.osgeo.org
   5  *
   6  * Copyright (C) 2009  Sandro Santilli <strk@keybit.net>
   7  *
   8  * This is free software; you can redistribute and/or modify it under
   9  * the terms of the GNU Lesser General Public Licence as published
  10  * by the Free Software Foundation.
  11  * See the COPYING file for more information.
  12  *
  13  **********************************************************************
  14  *
  15  * Last port: algorithm/distance/DistanceToPoint.java 1.1 (JTS-1.9)
  16  *
  17  **********************************************************************/
  18
  19 #include <geos/algorithm/distance/DistanceToPoint.h>
  20 #include <geos/algorithm/distance/PointPairDistance.h>
  21 #include <geos/geom/Coordinate.h>
  22 #include <geos/geom/CoordinateSequence.h>
  23 #include <geos/geom/LineSegment.h>
  24 #include <geos/geom/LineString.h>
  25 #include <geos/geom/Polygon.h>
  26 #include <geos/geom/GeometryCollection.h>
  27
  28 #include <typeinfo> // for dynamic_cast
  29 #include <cassert>
  30
  31 using namespace geos::geom;
  32
  33 namespace geos {
  34 namespace algorithm { // geos.algorithm
  35 namespace distance { // geos.algorithm.distance
  36
  37 /* public static */
  38 void
  39 DistanceToPoint::computeDistance(const geom::Geometry& geom,
  40                                           const geom::Coordinate& pt,
  41                                           PointPairDistance& ptDist)
  42 {
  43         if ( const LineString* ls = dynamic_cast<const LineString*>(&geom) )
  44         {
  45                 computeDistance(*ls, pt, ptDist);
  46         }
  47         else if ( const Polygon* pl = dynamic_cast<const Polygon*>(&geom) )
  48         {
  49                 computeDistance(*pl, pt, ptDist);
  50         }
  51         else if ( const GeometryCollection* gc = dynamic_cast<const GeometryCollection*>(&geom) )
  52         {
  53                 for (size_t i = 0; i < gc->getNumGeometries(); i++)
  54                 {
  55                         const Geometry* g = gc->getGeometryN(i);
  56                         computeDistance(*g, pt, ptDist);
  57                 }
  58         }
  59         else
  60         {
  61                 // assume geom is Point
  62                 ptDist.setMinimum(*(geom.getCoordinate()), pt);
  63         }
  64 }
  65
  66 /* public static */
  67 void
  68 DistanceToPoint::computeDistance(const geom::LineString& line,
  69                                           const geom::Coordinate& pt,
  70                                           PointPairDistance& ptDist)
  71 {
  72         const CoordinateSequence* coordsRO = line.getCoordinatesRO();
  73         const CoordinateSequence& coords = *coordsRO;
  74
  75         size_t npts = coords.size();
  76         if ( ! npts ) return; // can this ever be ?
  77
  78         LineSegment tempSegment;
  79         Coordinate closestPt;
  80
  81         Coordinate* segPts[2] = { &(tempSegment.p0), &(tempSegment.p1) };
  82         tempSegment.p0 = coords.getAt(0);
  83         for (size_t i=1; i<npts; ++i)
  84         {
  85                 *(segPts[i%2]) = coords.getAt(i);
  86
  87                 // this is somewhat inefficient - could do better
  88                 tempSegment.closestPoint(pt, closestPt);
  89                 ptDist.setMinimum(closestPt, pt);
  90         }
  91 }
  92
  93 /* public static */
  94 void
  95 DistanceToPoint::computeDistance(const geom::LineSegment& segment,
  96                                           const geom::Coordinate& pt,
  97                                           PointPairDistance& ptDist)
  98 {
  99         Coordinate closestPt;
 100         segment.closestPoint(pt, closestPt);
 101         ptDist.setMinimum(closestPt, pt);
 102 }
 103
 104 /* public static */
 105 void
 106 DistanceToPoint::computeDistance(const geom::Polygon& poly,
 107                                           const geom::Coordinate& pt,
 108                                           PointPairDistance& ptDist)
 109 {
 110         computeDistance(*(poly.getExteriorRing()), pt, ptDist);
 111         for (size_t i=0, n=poly.getNumInteriorRing(); i<n; ++i)
 112         {
 113                 computeDistance(*(poly.getInteriorRingN(i)), pt, ptDist);
 114         }
 115 }
 116
 117
 118 } // namespace geos.algorithm.distance
 119 } // namespace geos.algorithm
 120 } // namespace geos
 121