[geos-commits] r2072 - trunk/source/algorithm

[svn_geos at osgeo.org]

Author: benjubb
Date: 2007-12-21 15:50:50 -0500 (Fri, 21 Dec 2007)
New Revision: 2072

Added:
   trunk/source/algorithm/RayCrossingCounter.cpp
Log:


Added: trunk/source/algorithm/RayCrossingCounter.cpp
===================================================================
--- trunk/source/algorithm/RayCrossingCounter.cpp	                        (rev 0)
+++ trunk/source/algorithm/RayCrossingCounter.cpp	2007-12-21 20:50:50 UTC (rev 2072)
@@ -0,0 +1,157 @@
+/**********************************************************************
+ * $Id:
+ *
+ * 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/algorithm/RayCrossingCounter.h>
+#include <geos/algorithm/RobustDeterminant.h>
+#include <geos/geom/Geometry.h>
+#include <geos/geom/Location.h>
+#include <geos/geom/Coordinate.h>
+#include <geos/geom/CoordinateSequence.h>
+
+
+namespace geos {
+namespace algorithm {
+//
+// private:
+//
+
+//
+// protected:
+//
+
+//
+// public:
+//
+/*static*/ int 
+RayCrossingCounter::locatePointInRing( const geom::Coordinate * point, const geom::CoordinateSequence * ring) 
+{
+	RayCrossingCounter * rcc = new RayCrossingCounter( point);
+
+	for (int i = 1, ni = ring->size(); i < ni; i++) 
+	{
+		const geom::Coordinate & p1 = (*ring)[ i ];
+		const geom::Coordinate & p2 = (*ring)[ i - 1 ];
+
+		rcc->countSegment( &p1, &p2);
+
+		if ( rcc->isOnSegment() )
+			return rcc->getLocation();
+	}
+	return rcc->getLocation();
+}
+
+
+void 
+RayCrossingCounter::countSegment( const geom::Coordinate * p1, const geom::Coordinate * p2) 
+{
+	// For each segment, check if it crosses 
+	// a horizontal ray running from the test point in the positive x direction.
+	
+	// check if the segment is strictly to the left of the test point
+	if (p1->x < point->x && p2->x < point->x)
+		return;
+	
+	// check if the point is equal to the current ring vertex
+	if (point->x == p2->x && point->y == p2->y) 
+	{
+		isPointOnSegment = true;
+		return;
+	}
+
+	// For horizontal segments, check if the point is on the segment.
+	// Otherwise, horizontal segments are not counted.
+	if (p1->y == point->y && p2->y == point->y) 
+	{
+		double minx = p1->x;
+		double maxx = p2->x;
+
+		if (minx > maxx) 
+		{
+			minx = p2->x;
+			maxx = p1->x;
+		}
+		
+		if (point->x >= minx && point->x <= maxx) 
+			isPointOnSegment = true;
+
+		return;
+	}
+
+	// Evaluate all non-horizontal segments which cross a horizontal ray to the
+	// right of the test pt. To avoid double-counting shared vertices, we use the
+	// convention that
+	// - an upward edge includes its starting endpoint, and excludes its
+	//   final endpoint
+	// - a downward edge excludes its starting endpoint, and includes its
+	//   final endpoint
+	if (((p1->y > point->y) && (p2->y <= point->y)) ||
+		((p2->y > point->y) && (p1->y <= point->y)) ) 
+	{
+		// translate the segment so that the test point lies on the origin
+		double x1 = p1->x - point->x;
+		double y1 = p1->y - point->y;
+		double x2 = p2->x - point->x;
+		double y2 = p2->y - point->y;
+
+		// The translated segment straddles the x-axis. Compute the sign of the
+		// ordinate of intersection with the x-axis. (y2 != y1, so denominator
+		// will never be 0.0)
+		double xIntSign = RobustDeterminant::signOfDet2x2( x1, y1, x2, y2);
+
+		if (xIntSign == 0.0) 
+		{
+			isPointOnSegment = true;
+			return;
+		}
+
+		if (y2 < y1)
+			xIntSign = -xIntSign;
+
+		// The segment crosses the ray if the sign is strictly positive.
+		if (xIntSign > 0.0) 
+			crossingCount++;
+	}
+}
+
+
+int 
+RayCrossingCounter::getLocation() 
+{
+	if (isPointOnSegment)
+		return geom::Location::BOUNDARY;
+
+	// The point is in the interior of the ring if the number of X-crossings is
+	// odd.
+	if ((crossingCount % 2) == 1)
+		return geom::Location::INTERIOR;
+	
+	return geom::Location::EXTERIOR;
+}
+
+
+bool 
+RayCrossingCounter::isPointInPolygon()
+{
+	return getLocation() != geom::Location::EXTERIOR;
+}
+
+
+} // geos::algorithm
+} // geos
+
+/**********************************************************************
+ * $Log$
+ *
+ **********************************************************************/


Property changes on: trunk/source/algorithm/RayCrossingCounter.cpp
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