validate polygons from ways

geom/geos/geos.go

@@ -13,9 +13,11 @@ extern void initGEOS_debug();
 import "C"
 
 import (
-	"github.com/omniscale/imposm3/logging"
+	"errors"
 	"runtime"
 	"unsafe"
+
+	"github.com/omniscale/imposm3/logging"
 )
 
 var log = logging.NewLogger("GEOS")
@@ -268,6 +270,19 @@ func (this *Geos) Equals(a, b *Geom) bool {
 	return false
 }
 
+func (g *Geos) MakeValid(geom *Geom) (*Geom, error) {
+	if g.IsValid(geom) {
+		return geom, nil
+	}
+	fixed := g.Buffer(geom, 0)
+	if fixed == nil {
+		return nil, errors.New("Error while fixing geom with buffer(0)")
+	}
+	g.Destroy(geom)
+
+	return fixed, nil
+}
+
 func (this *Geom) Area() float64 {
 	var area C.double
 	if ret := C.GEOSArea(this.v, &area); ret == 1 {

geom/multipolygon.go

@@ -196,13 +196,10 @@ func buildRelGeometry(g *geos.Geos, rel *element.Relation, rings []*ring) (*geos
 			return nil, errors.New("Error while building multi-polygon.")
 		}
 	}
-	if !g.IsValid(result) {
-		buffered := g.Buffer(result, 0)
-		if buffered == nil {
-			return nil, errors.New("Error while fixing geom with buffer(0)")
-		}
-		g.Destroy(result)
-		result = buffered
+	var err error
+	result, err = g.MakeValid(result)
+	if err != nil {
+		return nil, err
 	}
 
 	g.DestroyLater(result)

test/complete_db_test.py

@@ -252,10 +252,10 @@ def test_duplicate_ids():
 def test_generalized_banana_polygon_is_valid():
     """Generalized polygons are valid."""
     park = t.query_row(t.db_conf, 'osm_landusages', 7101)
-    # geometry is not valid
-    assert not park['geometry'].is_valid, park
+    # geometry is valid
+    assert park['geometry'].is_valid, park
     park = t.query_row(t.db_conf, 'osm_landusages_gen0', 7101)
-    # but simplified geometies are valid
+    # simplified geometies are valid too
     assert park['geometry'].is_valid, park
     park = t.query_row(t.db_conf, 'osm_landusages_gen1', 7101)
     assert park['geometry'].is_valid, park

writer/ways.go

@@ -129,6 +129,9 @@ func (ww *WayWriter) buildAndInsert(g *geos.Geos, w *element.Way, matches []mapp
 
 	if isPolygon {
 		geosgeom, err = geomp.Polygon(g, way.Nodes)
+		if err == nil {
+			geosgeom, err = g.MakeValid(geosgeom)
+		}
 	} else {
 		geosgeom, err = geomp.LineString(g, way.Nodes)
 	}