[geos-commits] r3444 - in trunk: include/geos/algorithm src/algorithm

[svn_geos at osgeo.org]

Author: strk
Date: 2011-07-20 08:40:27 -0700 (Wed, 20 Jul 2011)
New Revision: 3444

Modified:
   trunk/include/geos/algorithm/ConvexHull.h
   trunk/include/geos/algorithm/ConvexHull.inl
   trunk/src/algorithm/ConvexHull.cpp
Log:
Port JTS robustness fix for ConvexHull (ticket #457)

Modified: trunk/include/geos/algorithm/ConvexHull.h
===================================================================
--- trunk/include/geos/algorithm/ConvexHull.h	2011-07-20 14:32:26 UTC (rev 3443)
+++ trunk/include/geos/algorithm/ConvexHull.h	2011-07-20 15:40:27 UTC (rev 3444)
@@ -4,6 +4,7 @@
  * GEOS - Geometry Engine Open Source
  * http://geos.refractions.net
  *
+ * Copyright (C) 2011 Sandro Santilli <strk at keybit.net>
  * Copyright (C) 2005-2006 Refractions Research Inc.
  * Copyright (C) 2001-2002 Vivid Solutions Inc.
  *
@@ -12,6 +13,10 @@
  * by the Free Software Foundation. 
  * See the COPYING file for more information.
  *
+ **********************************************************************
+ *
+ * Last port: algorithm/ConvexHull.java r407 (JTS-1.12+)
+ *
  **********************************************************************/
 
 #ifndef GEOS_ALGORITHM_CONVEXHULL_H
@@ -85,15 +90,19 @@
 	 * vertices is not 100% robust, this does not affect the
 	 * robustness of the convex hull.
 	 *
+	 * To satisfy the requirements of the Graham Scan algorithm,
+	 * the resulting array has at least 3 entries.
+	 *
 	 * @param pts The vector of const Coordinate pointers
-	 *            to be reduced
+	 *            to be reduced (to at least 3 elements)
 	 *
-	 *
 	 * WARNING: the parameter will be modified
 	 *
 	 */
 	void reduce(geom::Coordinate::ConstVect &pts);
 
+	/// parameter will be modified
+	void padArray3(geom::Coordinate::ConstVect &pts);
 
 	/// parameter will be modified
 	void preSort(geom::Coordinate::ConstVect &pts);

Modified: trunk/include/geos/algorithm/ConvexHull.inl
===================================================================
--- trunk/include/geos/algorithm/ConvexHull.inl	2011-07-20 14:32:26 UTC (rev 3443)
+++ trunk/include/geos/algorithm/ConvexHull.inl	2011-07-20 15:40:27 UTC (rev 3444)
@@ -11,6 +11,10 @@
  * by the Free Software Foundation. 
  * See the COPYING file for more information.
  *
+ **********************************************************************
+ *
+ * Last port: algorithm/ConvexHull.java r407 (JTS-1.12+)
+ *
  **********************************************************************/
 
 #ifndef GEOS_ALGORITHM_CONVEXHULL_INL

Modified: trunk/src/algorithm/ConvexHull.cpp
===================================================================
--- trunk/src/algorithm/ConvexHull.cpp	2011-07-20 14:32:26 UTC (rev 3443)
+++ trunk/src/algorithm/ConvexHull.cpp	2011-07-20 15:40:27 UTC (rev 3444)
@@ -4,8 +4,9 @@
  * GEOS - Geometry Engine Open Source
  * http://geos.refractions.net
  *
+ * Copyright (C) 2011 Sandro Santilli <strk at keybit.net>
+ * Copyright (C) 2005-2006 Refractions Research Inc.
  * Copyright (C) 2001-2002 Vivid Solutions Inc.
- * Copyright (C) 2005 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
@@ -14,7 +15,7 @@
  *
  **********************************************************************
  *
- * Last port: algorithm/ConvexHull.java rev. 1.26 (JTS-1.7)
+ * Last port: algorithm/ConvexHull.java r407 (JTS-1.12+)
  *
  **********************************************************************/
 
@@ -208,9 +209,19 @@
 	}
 
 	inputPts.assign(reducedSet.begin(), reducedSet.end());
- 
+
+	if ( inputPts.size() < 3 ) padArray3(inputPts);
 }
 
+/* private */
+void
+ConvexHull::padArray3(geom::Coordinate::ConstVect &pts)
+{
+  for (size_t i = pts.size(); i < 3; ++i) {
+    pts.push_back(pts[0]);
+  }
+}
+
 Geometry*
 ConvexHull::getConvexHull()
 {
@@ -284,8 +295,9 @@
 	for(size_t i=3, n=c.size(); i<n; ++i)
 	{
 		const Coordinate *p = ps.back(); ps.pop_back();
-		while (CGAlgorithms::computeOrientation(*(ps.back()),
-				*p, *(c[i])) > 0)
+		while (!ps.empty() && 
+			CGAlgorithms::computeOrientation(
+		    *(ps.back()), *p, *(c[i])) > 0)
 		{
 			p = ps.back(); ps.pop_back();
 		}