From: Raúl Marín Rodríguez <rmrodriguez@carto.com>
Date: Wed, 30 Jan 2019 13:35:17 +0000 (+0000)
Subject: ST_AsMVTGeom: Fix bug that oversimplified vertical or horizontal lines
X-Git-Tag: 3.0.0alpha1~171
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=30fe210917713755b4f50f867caf68983cad8394;p=postgis

ST_AsMVTGeom: Fix bug that oversimplified vertical or horizontal lines

References #4294
Closes https://github.com/postgis/postgis/pull/367



git-svn-id: http://svn.osgeo.org/postgis/trunk@17219 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/postgis/lwgeom_out_mvt.c b/postgis/lwgeom_out_mvt.c
index 616601199..6e992b00e 100644
--- a/postgis/lwgeom_out_mvt.c
+++ b/postgis/lwgeom_out_mvt.c
@@ -95,15 +95,12 @@ Datum ST_AsMVTGeom(PG_FUNCTION_ARGS)
 			/* Shortcut to drop geometries smaller than the resolution */
 			double geom_width = gserialized_box.xmax - gserialized_box.xmin;
 			double geom_height = gserialized_box.ymax - gserialized_box.ymin;
-			double geom_area = geom_width * geom_height;
 
-			double bounds_width = (bounds->xmax - bounds->xmin) / extent;
-			double bounds_height = (bounds->ymax - bounds->ymin) / extent;
-
-			/* We use 1/4th of the grid square area as the minimum resolution */
-			double min_resolution_area = bounds_width * bounds_height / 4.0;
-
-			if (geom_area < min_resolution_area)
+			/* We use half of the square height and width as limit: We use this
+			 * and not area so it works properly with lines */
+			double bounds_width = ((bounds->xmax - bounds->xmin) / extent) / 2.0;
+			double bounds_height = ((bounds->ymax - bounds->ymin) / extent) / 2.0;
+			if (geom_width < bounds_width && geom_height < bounds_height)
 			{
 				PG_RETURN_NULL();
 			}
diff --git a/regress/core/mvt.sql b/regress/core/mvt.sql
index 9b5507a74..2a21c0375 100644
--- a/regress/core/mvt.sql
+++ b/regress/core/mvt.sql
@@ -569,6 +569,15 @@ SELECT '#3922', St_Area(ST_AsMVTGeom(
 		true
 		));
 
+SELECT '#4294_Horizontal', ST_AsText(ST_AsMVTGeom(
+	ST_GeomFromText('MULTILINESTRING((0 0, 0 5))'),
+	ST_MakeBox2D(ST_Point(0, 0), ST_Point(10, 10)),
+	10, 0, true));
+
+SELECT '#4294_Vertical', ST_AsText(ST_AsMVTGeom(
+	ST_GeomFromText('MULTILINESTRING((0 0, 5 0))'),
+	ST_MakeBox2D(ST_Point(0, 0), ST_Point(10, 10)),
+	10, 0, true));
 
 -- Feature id encoding tests
 SELECT 'FI1', encode(ST_AsMVT(q, 'test', 4096, 'geom', 'c1'), 'base64') FROM (
diff --git a/regress/core/mvt_expected b/regress/core/mvt_expected
index c0e777182..fe13e2395 100644
--- a/regress/core/mvt_expected
+++ b/regress/core/mvt_expected
@@ -123,6 +123,8 @@ TU2
 ERROR:  pgis_asmvt_transfn: parameter row cannot be other than a rowtype
 TU3|
 #3922|6.5
+#4294_Horizontal|LINESTRING(0 10,0 5)
+#4294_Vertical|LINESTRING(0 10,5 10)
 FI1|GicKBHRlc3QSDggBEgIAABgBIgQJMt4/GgJjMiIGCgRhYmNkKIAgeAI=
 FI2|GicKBHRlc3QSDggBEgIAABgBIgQJMt4/GgJjMiIGCgRhYmNkKIAgeAI=
 FI3|GicKBHRlc3QSDggBEgIAABgBIgQJMt4/GgJjMiIGCgRhYmNkKIAgeAI=