hcoordinate.cpp

一个很好的vc底层代码

/**********************************************************************
 * $Id: HCoordinate.cpp,v 1.12 2004/11/29 16:05:33 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.
 *
 **********************************************************************/

#include <geos/geosAlgorithm.h>
#include <geos/platform.h>

namespace geos {

/*
 * Computes the (approximate) intersection point between two line segments
 * using homogeneous coordinates.
 * 
 * Note that this algorithm is
 * not numerically stable; i.e. it can produce intersection points which
 * lie outside the envelope of the line segments themselves.  In order
 * to increase the precision of the calculation input points should be
 * normalized before passing them to this routine.
 */
Coordinate*
HCoordinate::intersection(Coordinate& p1,Coordinate& p2,Coordinate& q1,Coordinate& q2)
{
	auto_ptr<HCoordinate> intHCoord(new HCoordinate(HCoordinate(HCoordinate(p1),HCoordinate(p2)),HCoordinate(HCoordinate(q1),HCoordinate(q2))));
	return intHCoord->getCoordinate();
}

HCoordinate::HCoordinate(){
	x = 0.0;
	y = 0.0;
	w = 1.0;
}

HCoordinate::HCoordinate(double _x, double _y, double _w) {
	x = _x;
	y = _y;
	w = _w;
}

HCoordinate::HCoordinate(Coordinate& p) {
	x = p.x;
	y = p.y;
	w = 1.0;
}

HCoordinate::HCoordinate(HCoordinate p1, HCoordinate p2) {
	x = p1.y*p2.w - p2.y*p1.w;
	y = p2.x*p1.w - p1.x*p2.w;
	w = p1.x*p2.y - p2.x*p1.y;
}

double HCoordinate::getX() {
	double a = x/w;
	if (!FINITE(a))
	{
		throw new NotRepresentableException();
	}
	return a;
}

double
HCoordinate::getY()
{
	double a = y/w;
	if (!FINITE(a))
	{
		throw new NotRepresentableException();
	}
	return a;
}

Coordinate* HCoordinate::getCoordinate() {
	return new Coordinate(getX(),getY());
}

} // namespace geos

/**********************************************************************
 * $Log: HCoordinate.cpp,v $
 * Revision 1.12  2004/11/29 16:05:33  strk
 * Fixed a bug in LineIntersector::interpolateZ causing NaN values
 * to come out.
 * Handled dimensional collapses in ElevationMatrix.
 * Added ISNAN macro and changed ISNAN/FINITE macros to avoid
 * dispendious isnan() and finite() calls.
 *
 * Revision 1.11  2004/10/20 17:32:14  strk
 * Initial approach to 2.5d intersection()
 *
 * Revision 1.10  2004/07/02 13:28:26  strk
 * Fixed all #include lines to reflect headers layout change.
 * Added client application build tips in README.
 *
 * Revision 1.9  2003/11/07 01:23:42  pramsey
 * Add standard CVS headers licence notices and copyrights to all cpp and h
 * files.
 *
 *
 **********************************************************************/