src/geom/util/SineStarFactory.cpp

   1 /**********************************************************************
   2  *
   3  * GEOS - Geometry Engine Open Source
   4  * http://geos.osgeo.org
   5  *
   6  * Copyright (C) 2011 Sandro Santilli <strk@kbt.io
   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: geom/util/SineStarFactory.java r378 (JTS-1.12)
  16  *
  17  **********************************************************************/
  18
  19 #include <geos/geom/util/SineStarFactory.h>
  20 #include <geos/geom/Coordinate.h>
  21 #include <geos/geom/CoordinateSequenceFactory.h>
  22 #include <geos/geom/CoordinateSequence.h>
  23 #include <geos/geom/GeometryFactory.h>
  24 #include <geos/geom/Envelope.h>
  25 #include <geos/geom/Polygon.h>
  26 #include <geos/geom/LinearRing.h>
  27
  28 #include <vector>
  29 #include <cmath>
  30 #include <memory>
  31
  32 #ifndef M_PI
  33 #define M_PI        3.14159265358979323846
  34 #endif
  35
  36 using namespace std;
  37 //using namespace geos::geom;
  38
  39 namespace geos {
  40 namespace geom { // geos::geom
  41 namespace util { // geos::geom::util
  42
  43 /* public */
  44 auto_ptr<Polygon>
  45 SineStarFactory::createSineStar() const
  46 {
  47   auto_ptr<Envelope> env ( dim.getEnvelope() );
  48   double radius = env->getWidth() / 2.0;
  49
  50   double armRatio = armLengthRatio;
  51   if (armRatio < 0.0) armRatio = 0.0;
  52   if (armRatio > 1.0) armRatio = 1.0;
  53
  54   double armMaxLen = armRatio * radius;
  55   double insideRadius = (1 - armRatio) * radius;
  56
  57   double centreX = env->getMinX() + radius;
  58   double centreY = env->getMinY() + radius;
  59
  60   auto_ptr< vector<Coordinate> > pts ( new vector<Coordinate>(nPts+1) );
  61   int iPt = 0;
  62   for (int i = 0; i < nPts; i++) {
  63     // the fraction of the way thru the current arm - in [0,1]
  64     double ptArcFrac = (i / (double) nPts) * numArms;
  65     double armAngFrac = ptArcFrac - floor(ptArcFrac);
  66
  67     // the angle for the current arm - in [0,2Pi]
  68     // (each arm is a complete sine wave cycle)
  69     double armAng = 2 * M_PI * armAngFrac;
  70     // the current length of the arm
  71     double armLenFrac = (cos(armAng) + 1.0) / 2.0;
  72
  73     // the current radius of the curve (core + arm)
  74     double curveRadius = insideRadius + armMaxLen * armLenFrac;
  75
  76     // the current angle of the curve
  77     double ang = i * (2 * M_PI / nPts);
  78     double x = curveRadius * cos(ang) + centreX;
  79     double y = curveRadius * sin(ang) + centreY;
  80     (*pts)[iPt++] = coord(x, y);
  81   }
  82   (*pts)[iPt] = Coordinate((*pts)[0]);
  83
  84   auto_ptr<CoordinateSequence> cs (
  85     geomFact->getCoordinateSequenceFactory()->create( pts.release() )
  86   );
  87   auto_ptr<LinearRing> ring ( geomFact->createLinearRing( cs.release() ) );
  88   auto_ptr<Polygon> poly ( geomFact->createPolygon(ring.release(), 0) );
  89   return poly;
  90 }
  91
  92 } // namespace geos::geom::util
  93 } // namespace geos::geom
  94 } // namespace geos
  95