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- from cx_Oracle import CLOB
-
- from django.contrib.gis.db.backends.base.adapter import WKTAdapter
- from django.contrib.gis.geos import GeometryCollection, Polygon
-
-
- class OracleSpatialAdapter(WKTAdapter):
- input_size = CLOB
-
- def __init__(self, geom):
- """
- Oracle requires that polygon rings are in proper orientation. This
- affects spatial operations and an invalid orientation may cause
- failures. Correct orientations are:
- * Outer ring - counter clockwise
- * Inner ring(s) - clockwise
- """
- if isinstance(geom, Polygon):
- self._fix_polygon(geom)
- elif isinstance(geom, GeometryCollection):
- self._fix_geometry_collection(geom)
-
- self.wkt = geom.wkt
- self.srid = geom.srid
-
- def _fix_polygon(self, poly):
- """Fix single polygon orientation as described in __init__()."""
- if self._isClockwise(poly.exterior_ring):
- poly.exterior_ring = list(reversed(poly.exterior_ring))
-
- for i in range(1, len(poly)):
- if not self._isClockwise(poly[i]):
- poly[i] = list(reversed(poly[i]))
-
- return poly
-
- def _fix_geometry_collection(self, coll):
- """
- Fix polygon orientations in geometry collections as described in
- __init__().
- """
- for i, geom in enumerate(coll):
- if isinstance(geom, Polygon):
- coll[i] = self._fix_polygon(geom)
-
- def _isClockwise(self, coords):
- """
- A modified shoelace algorithm to determine polygon orientation.
- See https://en.wikipedia.org/wiki/Shoelace_formula.
- """
- n = len(coords)
- area = 0.0
- for i in range(n):
- j = (i + 1) % n
- area += coords[i][0] * coords[j][1]
- area -= coords[j][0] * coords[i][1]
- return area < 0.0
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