Commit 35db4ea0 authored by Raúl Marín Rodríguez's avatar Raúl Marín Rodríguez
Browse files

St_AsMVTGeom: Fix bug when clipping an invalid geometry 

If the geometry becomes invalid after simplifying, the clipping
could be invalid too. For those cases we drop the geometry.


git-svn-id: http://svn.osgeo.org/postgis/trunk@16856 b70326c6-7e19-0410-871a-916f4a2858ee
parent a8ba4a75

NEWS

+1 −0
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ PostGIS 3.0.0 
  - #4161, MVT: Drop geometries smaller than the resolution (Raúl Marín)

  - #4176, ST_Intersects supports GEOMETRYCOLLECTION (Darafei Praliaskouski)

  - #4181, St_AsMVTGeom: Avoid type changes due to validation (Raúl Marín)

  - #4183, St_AsMVTGeom: Drop invalid geometries after simplification (Raúl Marín)



PostGIS 2.5.0

2018/09/23

postgis/mvt.c

+23 −3
Original line number Diff line number Diff line
@@ -894,11 +894,31 @@ LWGEOM *mvt_geom(LWGEOM *lwgeom, const GBOX *gbox, uint32_t extent, uint32_t buf 
			double y0 = bgbox.ymin;

			double x1 = bgbox.xmax;

			double y1 = bgbox.ymax;

			lwgeom = lwgeom_clip_by_rect(lwgeom, x0, y0, x1, y1);

			const GBOX pre_clip_box = *lwgeom_get_bbox(lwgeom);

			LWGEOM *clipped_geom = lwgeom_clip_by_rect(lwgeom, x0, y0, x1, y1);

			if (clipped_geom == NULL || lwgeom_is_empty(clipped_geom))

			{

				POSTGIS_DEBUG(3, "mvt_geom: no geometry after clip");

			if (lwgeom == NULL || lwgeom_is_empty(lwgeom))

				return NULL;

			}

			/* For some polygons, the simplify step might have left them

			 * as invalid, which can cause clipping to return the complementary

			 * geometry of what it should */

			if ((lwgeom->type == POLYGONTYPE ||

				lwgeom->type == MULTIPOLYGONTYPE ||

				lwgeom->type == COLLECTIONTYPE) &&

			    !gbox_contains_2d(&pre_clip_box, lwgeom_get_bbox(clipped_geom)))

			{

				/* TODO: Adapt this when and if Exception Policies are introduced.

				 * Other options would be to fix the geometry and retry

				 * or to calculate the difference between the 2 boxes.

				 */

				POSTGIS_DEBUG(3, "mvt_geom: Invalid geometry after clipping");

				lwgeom_free(clipped_geom);

				return NULL;

			}

			lwgeom = clipped_geom;

		}

	}



	/* transform to tile coordinate space */

regress/mvt.sql

+8 −0
Original line number Diff line number Diff line
@@ -265,6 +265,14 @@ SELECT 'PG44', ST_AsEWKT(ST_AsMVTGeom( 
	16,

	true));



-- Invalid geometry after simplification with invalid clipping

SELECT 'PG45', ST_AsEWKT(ST_AsMVTGeom(

	'SRID=3857;MULTIPOLYGON(((-8231365.02893734 4980355.83678553,-8231394.82332406 4980186.31880185,-8231367.43081065 4979982.17443372,-8231396.69199339 4980227.59327083,-8231365.02893734 4980355.83678553)))'::geometry,

	'SRID=3857;POLYGON((-8238115.3789773 4970203.10870116,-8238115.3789773 4980063.48534995,-8228255.00232851 4980063.48534995,-8228255.00232851 4970203.10870116,-8238115.3789773 4970203.10870116))'::geometry,

	4096,

	16,

	true));



-- geometry encoding tests

SELECT 'TG1', encode(ST_AsMVT(q, 'test', 4096, 'geom'), 'base64') FROM (SELECT 1 AS c1,

	ST_AsMVTGeom(ST_GeomFromText('POINT(25 17)'),

regress/mvt_expected

+1 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ PG42 - OFF|LINESTRING(0 10,0 0,1 0) 
PG43 - ON |MULTIPOLYGON(((5 5,0 0,10 0,5 5)),((0 10,5 5,10 10,0 10)))

PG43 - OFF|MULTIPOLYGON(((5 5,-1 -1,11 -1,5 5)),((5 5,11 11,-1 11,5 5)))

PG44|

PG45|

TG1|GiEKBHRlc3QSDBICAAAYASIECTLePxoCYzEiAigBKIAgeAI=

TG2|GiMKBHRlc3QSDhICAAAYASIGETLePwIBGgJjMSICKAEogCB4Ag==

TG3|GiYKBHRlc3QSERICAAAYAiIJCQCAQArQD88PGgJjMSICKAEogCB4Ag==