centroidarea.cpp

一个很好的vc底层代码

/**********************************************************************
 * $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);
}

}