From: Sandro Santilli <strk@keybit.net>
Date: Sun, 11 Aug 2013 15:55:50 +0000 (+0000)
Subject: Require at least 8 edges to define a full circle (#2420)
X-Git-Tag: 2.2.0rc1~1411
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=3b821c1aabe7655b9eaef4b4028af1223a832b9b;p=postgis

Require at least 8 edges to define a full circle (#2420)

git-svn-id: http://svn.osgeo.org/postgis/trunk@11769 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/liblwgeom/lwsegmentize.c b/liblwgeom/lwsegmentize.c
index 4fa9671b9..b7858f4e4 100644
--- a/liblwgeom/lwsegmentize.c
+++ b/liblwgeom/lwsegmentize.c
@@ -16,6 +16,9 @@
 #include <string.h>
 
 #include "liblwgeom_internal.h"
+
+//#define POSTGIS_DEBUG_LEVEL 4
+
 #include "lwgeom_log.h"
 
 
@@ -551,9 +554,11 @@ pta_desegmentize(POINTARRAY *points, int type, int srid)
 	int found_arc = LW_FALSE;
 	int current_arc = 1;
 	int num_edges;
-	int edge_type = -1;
+	int edge_type; /* non-zero if edge is part of an arc */
 	int start, end;
 	LWCOLLECTION *outcol;
+	/* Minimum number of edges, per quadrant, required to define an arc */
+	const unsigned int min_quad_edges = 2;
 
 	/* Die on null input */
 	if ( ! points )
@@ -608,6 +613,24 @@ pta_desegmentize(POINTARRAY *points, int type, int srid)
 		/* Jump past all the edges that were added to the arc */
 		if ( found_arc )
 		{
+			/* Check if an arc was composed by enough edges to be
+			 * really considered an arc
+			 * See http://trac.osgeo.org/postgis/ticket/2420
+			 */
+			unsigned int arc_edges = j - 1 - i;
+			unsigned int num_quadrants = 1; /* silly guess, TODO: compute */
+			LWDEBUGF(4, "arc defined by %d edges found", arc_edges);
+			if ( a1.x == b.x && a1.y == b.y ) {
+				LWDEBUG(4, "arc is a circle");
+				num_quadrants = 4;
+			}
+			/* a1 is first point, b is last point */
+			if ( arc_edges < min_quad_edges * num_quadrants ) {
+				LWDEBUGF(4, "Not enough edges for a %d quadrants arc", num_quadrants);
+				for ( k = j-1; k >= i; k-- )
+					edges_in_arcs[k] = 0;
+			}
+
 			i = j-1;
 		}
 		else
diff --git a/regress/tickets.sql b/regress/tickets.sql
index d58ee794c..c516b6d3a 100644
--- a/regress/tickets.sql
+++ b/regress/tickets.sql
@@ -831,5 +831,7 @@ SELECT '#2415.2', ST_AsText(ST_Multi(
 
 SELECT '#2412', ST_AsText(ST_LineToCurve('LINESTRING(0 0,10 0,20 0)'));
 
+SELECT '#2430', ST_AsText(ST_LineToCurve('LINESTRING(0 0,10 0,10 10,0 10,0 0)'));
+
 -- Clean up
 DELETE FROM spatial_ref_sys;
diff --git a/regress/tickets_expected b/regress/tickets_expected
index 1084bae7c..82130cf80 100644
--- a/regress/tickets_expected
+++ b/regress/tickets_expected
@@ -247,3 +247,4 @@ ERROR:  invalid GML representation
 #2415.1|MULTICURVE(COMPOUNDCURVE((0 0,10 0),CIRCULARSTRING(10 0,15 1,20 10)))
 #2415.2|MULTISURFACE(CURVEPOLYGON(CIRCULARSTRING(10 0,15 1,20 0,18 5,20 10,10 10,10 0)))
 #2412|LINESTRING(0 0,10 0,20 0)
+#2430|LINESTRING(0 0,10 0,10 10,0 10,0 0)