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/**********************************************************************
* $Id: CentroidArea.cpp,v 1.14 2004/07/08 19:34:49 strk Exp $
*
* GEOS - Geometry Engine Open Source
* http://geos.refractions.net
*
* Copyright (C) 2001-2002 Vivid Solutions Inc.
*
* This is free software; you can redistribute and/or modify it under
* the terms of the GNU Lesser General Public Licence as published
* by the Free Software Foundation.
* See the COPYING file for more information.
*
**********************************************************************
* $Log: CentroidArea.cpp,v $
* Revision 1.14 2004/07/08 19:34:49 strk
* Mirrored JTS interface of CoordinateSequence, factory and
* default implementations.
* Added DefaultCoordinateSequenceFactory::instance() function.
*
* Revision 1.13 2004/07/02 13:28:26 strk
* Fixed all #include lines to reflect headers layout change.
* Added client application build tips in README.
*
* Revision 1.12 2004/05/17 07:42:54 strk
* CentroidArea::add(const Geometry *geom) uses dynamic_cast
*
* Revision 1.11 2004/03/17 02:00:33 ybychkov
* "Algorithm" upgraded to JTS 1.4
*
* Revision 1.10 2003/11/07 01:23:42 pramsey
* Add standard CVS headers licence notices and copyrights to all cpp and h
* files.
*
* Revision 1.9 2003/10/16 08:50:00 strk
* Memory leak fixes. Improved performance by mean of more calls to
* new getCoordinatesRO() when applicable.
*
* Revision 1.8 2003/10/13 15:39:03 strk
* Fixed some leak or fault flips (forced copy of a single coordinate)
*
* Revision 1.7 2003/10/11 01:56:08 strk
*
* Code base padded with 'const' keywords ;)
*
**********************************************************************/
#include <geos/geosAlgorithm.h>
#include <geos/platform.h>
#include <typeinfo>
namespace geos {
CentroidArea::CentroidArea() {
basePt=NULL;
cga=new RobustCGAlgorithms();
triangleCent3=new Coordinate();
areasum2=0;
cg3=new Coordinate();
}
CentroidArea::~CentroidArea() {
delete cga;
delete triangleCent3;
delete cg3;
delete basePt;
}
/**
* Adds the area defined by a Geometry to the centroid total.
* If the geometry has no area it does not contribute to the centroid.
*
* @param geom the geometry to add
*/
void CentroidArea::add(const Geometry *geom) {
if(const Polygon *poly=dynamic_cast<const Polygon*>(geom)) {
setBasePoint(&(poly->getExteriorRing()->getCoordinateN(0)));
add(poly);
}
else if(const GeometryCollection *gc=dynamic_cast<const GeometryCollection*>(geom))
{
for(int i=0;i<gc->getNumGeometries();i++) {
add(gc->getGeometryN(i));
}
}
}
/**
* Adds the area defined by an array of
* coordinates. The array must be a ring;
* i.e. end with the same coordinate as it starts with.
* @param ring an array of {@link Coordinate}s
*/
void CentroidArea::add(const CoordinateSequence *ring) {
setBasePoint(&(ring->getAt(0)));
addShell(ring);
}
Coordinate* CentroidArea::getCentroid() const {
Coordinate *cent = new Coordinate();
cent->x = cg3->x/3.0/areasum2;
cent->y = cg3->y/3.0/areasum2;
return cent;
}
void CentroidArea::setBasePoint(const Coordinate *newbasePt)
{
if(basePt==NULL) basePt=new Coordinate(*newbasePt);
}
void CentroidArea::add(const Polygon *poly) {
addShell(poly->getExteriorRing()->getCoordinatesRO());
for(int i=0;i<poly->getNumInteriorRing();i++) {
addHole(poly->getInteriorRingN(i)->getCoordinatesRO());
}
}
void CentroidArea::addShell(const CoordinateSequence *pts) {
bool isPositiveArea=!CGAlgorithms::isCCW(pts);
for(int i=0;i<pts->getSize()-1;i++) {
addTriangle(*basePt,pts->getAt(i),pts->getAt(i+1),isPositiveArea);
}
}
void CentroidArea::addHole(const CoordinateSequence *pts){
bool isPositiveArea=CGAlgorithms::isCCW(pts);
for(int i=0;i<pts->getSize()-1;i++) {
addTriangle(*basePt,pts->getAt(i),pts->getAt(i+1),isPositiveArea);
}
}
inline void
CentroidArea::addTriangle(const Coordinate &p0, const Coordinate &p1,
const Coordinate &p2,bool isPositiveArea)
{
double sign=(isPositiveArea)?1.0:-1.0;
centroid3(p0,p1,p2,triangleCent3);
double area2res=area2(p0,p1,p2);
cg3->x+=sign*area2res*triangleCent3->x;
cg3->y+=sign*area2res*triangleCent3->y;
areasum2+=sign*area2res;
}
/**
* Returns three times the centroid of the triangle p1-p2-p3.
* The factor of 3 is
* left in to permit division to be avoided until later.
*/
inline void
CentroidArea::centroid3(const Coordinate &p1, const Coordinate &p2,
const Coordinate &p3, Coordinate *c)
{
c->x=p1.x+p2.x+p3.x;
c->y=p1.y+p2.y+p3.y;
}
/**
* Returns twice the signed area of the triangle p1-p2-p3,
* positive if a,b,c are oriented ccw, and negative if cw.
*/
inline double CentroidArea::area2(const Coordinate &p1, const Coordinate &p2, const Coordinate &p3){
return (p2.x-p1.x)*(p3.y-p1.y)-(p3.x-p1.x)*(p2.y-p1.y);
}
}
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