Merge pull request #368 from tilezen/zerebubuth/fix-boundaries-orient-multipolygon

Add utility function to orient MultiPolygons.

Author: zerebubuth

tests/test_query_rawr.py

@@ -820,6 +820,48 @@ def _tile_triangle(bounds):
         # check no area
         self.assertIsNone(props.get('area'))
 
+    def test_boundaries_from_multipolygons(self):
+        # check that the boundary extraction code also works for multipolygons
+        from shapely.geometry import Polygon, MultiPolygon
+
+        def _tile_squares(bounds):
+            # maxy      +----+
+            #           | b  |
+            # midy +----+----+
+            #      | a  |
+            # miny +----+
+            #      minx midx maxx
+
+            minx, miny, maxx, maxy = bounds
+            midx = 0.5 * (minx + maxx)
+            midy = 0.5 * (miny + maxy)
+
+            a = Polygon([
+                [minx, miny],
+                [minx, midy],
+                [midx, midy],
+                [midx, miny],
+                [minx, miny],
+            ])
+
+            b = Polygon([
+                [midx, midy],
+                [midx, maxy],
+                [maxx, maxy],
+                [maxx, midy],
+                [midy, midy],
+            ])
+
+            return MultiPolygon([a, b])
+
+        read_rows = self._fetch_data(_tile_squares, 'planet_osm_polygon')
+
+        self.assertEqual(len(read_rows), 1)
+        props = read_rows[0]['__boundaries_properties__']
+        self.assertEqual(props.get('boundary'), 'administrative')
+        # check no area
+        self.assertIsNone(props.get('area'))
+
 
 class TestBufferedLand(RawrTestCase):
 

tilequeue/query/rawr.py

@@ -1,6 +1,7 @@
 from collections import namedtuple, defaultdict
 from shapely.geometry import box
 from shapely.geometry import MultiLineString
+from shapely.geometry import MultiPolygon
 from shapely.geometry.polygon import orient
 from shapely.wkb import loads as wkb_loads
 from tilequeue.query.common import layer_properties
@@ -612,6 +613,25 @@ def _lines_only(shape):
         return MultiLineString(lines)
 
 
+def _orient(shape):
+    """
+    The Shapely version of the orient function appears to only work on
+    Polygons, and fails on MultiPolygons. This is a quick wrapper to allow
+    orienting of either.
+    """
+
+    assert shape.geom_type in ('Polygon', 'MultiPolygon')
+
+    if shape.geom_type == 'Polygon':
+        return orient(shape)
+
+    else:
+        polys = []
+        for geom in shape.geoms:
+            polys.append(orient(geom))
+        return MultiPolygon(polys)
+
+
 class RawrTile(object):
 
     def __init__(self, layers, tables, tile_pyramid, label_placement_layers,
@@ -757,7 +777,7 @@ def _parse_row(self, zoom, unpadded_bounds, bbox, source, fid, shape,
                 # make sure boundary rings are oriented in the correct
                 # direction; anti-clockwise for outers and clockwise for
                 # inners, which means the interior should be on the left.
-                boundaries_shape = orient(shape).boundary
+                boundaries_shape = _orient(shape).boundary
 
                 # make sure it's only lines, post-intersection. a polygon-line
                 # intersection can return points as well as lines. however,