[geos-commits] r2060 - trunk/source/headers/geos/algorithm

[svn_geos at osgeo.org]

Author: benjubb
Date: 2007-12-21 15:37:32 -0500 (Fri, 21 Dec 2007)
New Revision: 2060

Added:
   trunk/source/headers/geos/algorithm/RayCrossingCounter.h
Log:
Added from JTS 1.9 to support prepared geometry 

Added: trunk/source/headers/geos/algorithm/RayCrossingCounter.h
===================================================================
--- trunk/source/headers/geos/algorithm/RayCrossingCounter.h	                        (rev 0)
+++ trunk/source/headers/geos/algorithm/RayCrossingCounter.h	2007-12-21 20:37:32 UTC (rev 2060)
@@ -0,0 +1,142 @@
+/**********************************************************************
+ * $Id
+ *
+ * GEOS - Geometry Engine Open Source
+ * http://geos.refractions.net
+ *
+ * Copyright (C) 2006 Refractions Research 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.
+ *
+ *
+ **********************************************************************/
+
+#ifndef GEOS_ALGORITHM_RAYCROSSINGCOUNTER_H
+#define GEOS_ALGORITHM_RAYCROSSINGCOUNTER_H
+
+
+// forward declarations
+namespace geos {
+	namespace geom {
+		class Coordinate;
+		class CoordinateSequence;
+	}
+}
+
+
+namespace geos {
+namespace algorithm {
+
+/**
+ * Counts the number of segments crossed by a horizontal ray extending to the right
+ * from a given point, in an incremental fashion.
+ * This can be used to determine whether a point lies in a {@link Polygonal} geometry.
+ * The class determines the situation where the point lies exactly on a segment.
+ * When being used for Point-In-Polygon determination, this case allows short-circuiting
+ * the evaluation.
+ * <p>
+ * This class handles polygonal geometries with any number of shells and holes.
+ * The orientation of the shell and hole rings is unimportant.
+ * In order to compute a correct location for a given polygonal geometry, 
+ * it is essential that <b>all</b> segments are counted which
+ * <ul>
+ * <li>touch the ray 
+ * <li>lie in in any ring which may contain the point
+ * </ul>
+ * The only exception is when the point-on-segment situation is detected, in which
+ * case no further processing is required.
+ * The implication of the above rule is that segments 
+ * which can be a priori determined to <i>not</i> touch the ray
+ * (i.e. by a test of their bounding box or Y-extent) 
+ * do not need to be counted.  This allows for optimization by indexing.
+ * 
+ * @author Martin Davis
+ *
+ */
+class RayCrossingCounter 
+{
+private:
+	const geom::Coordinate * point;
+	
+	int crossingCount;
+	
+	// true if the test point lies on an input segment
+	bool isPointOnSegment;
+
+protected:
+public:
+	/**
+	 * Determines the {@link Location} of a point in a ring.
+	 * This method is an exemplar of how to use this class.
+	 * 
+	 * @param p the point to test
+	 * @param ring an array of Coordinates forming a ring 
+	 * @return the location of the point in the ring
+	 */
+	static int locatePointInRing( const geom::Coordinate * p, const geom::CoordinateSequence * ring);
+
+	RayCrossingCounter( const geom::Coordinate * point)
+	:	point( point),
+		crossingCount( 0),
+		isPointOnSegment( false)
+	{ }
+	
+	/**
+	 * Counts a segment
+	 * 
+	 * @param p1 an endpoint of the segment
+	 * @param p2 another endpoint of the segment
+	 */
+	void countSegment( const geom::Coordinate * p1, const geom::Coordinate * p2);
+	
+	/**
+	 * Reports whether the point lies exactly on one of the supplied segments.
+	 * This method may be called at any time as segments are processed.
+	 * If the result of this method is <tt>true</tt>, 
+	 * no further segments need be supplied, since the result
+	 * will never change again.
+	 * 
+	 * @return true if the point lies exactly on a segment
+	 */
+	bool isOnSegment() 
+	{ 
+		return isPointOnSegment; 
+	}
+	
+	/**
+	 * Gets the {@link Location} of the point relative to 
+	 * the ring, polygon
+	 * or multipolygon from which the processed segments were provided.
+	 * <p>
+	 * This method only determines the correct location 
+	 * if <b>all</b> relevant segments must have been processed. 
+	 * 
+	 * @return the Location of the point
+ 	 */
+	int getLocation();
+    
+	/**
+	 * Tests whether the point lies in or on 
+	 * the ring, polygon
+	 * or multipolygon from which the processed segments were provided.
+	 * <p>
+	 * This method only determines the correct location 
+	 * if <b>all</b> relevant segments must have been processed. 
+	 * 
+	 * @return true if the point lies in or on the supplied polygon
+	 */
+	bool isPointInPolygon();
+
+};
+
+} // geos::algorithm
+} // geos
+
+#endif // GEOS_ALGORITHM_RAYCROSSINGCOUNTER_H
+/**********************************************************************
+ * $Log$
+ **********************************************************************/
+


Property changes on: trunk/source/headers/geos/algorithm/RayCrossingCounter.h
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