Hi List,
I am looking into the Shapely library, it's great. I do need to, however,
access other functionality from libgeos, and have been flailing around trying
coerce ctypes and GEOS to work together. I was about to post a question... but
found the/a solution, so I'm posting it here for posterity.
For it to work, shapely/geometry/__init__.py must include the following:
from base import geom_factory
---------------- test_polygonize.py --------------------
import shapely
from shapely.geometry import LineString, geom_factory
from shapely.wkt import loads
from shapely.geos import lgeos
from ctypes import byref, c_void_p, c_double
def Polygonize(linestr_array):
"""
Finds all valid polygons defined by an array of LineString objects.
"""
geom_array_type = c_void_p * len(linestr_array)
geom_array = geom_array_type()
for i,l in enumerate(linestr_array):
geom_array[i] = l._geom
#a = c_double()
#lgeos.GEOSLength(l._geom, byref(a))
#print l._geom, a
product = lgeos.GEOSPolygonize(byref(geom_array), len(linestr_array))
return geom_factory(product)
def _test():
lines = [LineString([[0, 0], [1, 1]]),
LineString([[0, 0], [0, 1]]),
LineString([[0, 1], [1, 1]]),
LineString([[1, 1], [1, 0]]),
LineString([[1, 0], [0, 0]])]
print Polygonize(lines)
if __name__ == "__main__":
_test()
---------------------------------------------------
Cheers,
Nino
Nino Walker :: Urban Mapping, Inc.
690 Fifth Street Suite 200 :: San Francisco CA 94107
www.urbanmapping.com
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