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