70 lines
2.7 KiB
Python
70 lines
2.7 KiB
Python
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"""
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The goal of this module is to be a ctypes wrapper around the GEOS library
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that will work on both *NIX and Windows systems. Specifically, this uses
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the GEOS C api.
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I have several motivations for doing this:
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(1) The GEOS SWIG wrapper is no longer maintained, and requires the
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installation of SWIG.
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(2) The PCL implementation is over 2K+ lines of C and would make
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PCL a requisite package for the GeoDjango application stack.
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(3) Windows and Mac compatibility becomes substantially easier, and does not
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require the additional compilation of PCL or GEOS and SWIG -- all that
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is needed is a Win32 or Mac compiled GEOS C library (dll or dylib)
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in a location that Python can read (e.g. 'C:\Python25').
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In summary, I wanted to wrap GEOS in a more maintainable and portable way using
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only Python and the excellent ctypes library (now standard in Python 2.5).
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In the spirit of loose coupling, this library does not require Django or
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GeoDjango. Only the GEOS C library and ctypes are needed for the platform
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of your choice.
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For more information about GEOS:
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http://geos.refractions.net
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For more info about PCL and the discontinuation of the Python GEOS
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library see Sean Gillies' writeup (and subsequent update) at:
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http://zcologia.com/news/150/geometries-for-python/
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http://zcologia.com/news/429/geometries-for-python-update/
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"""
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from django.contrib.gis.geos.base import GEOSGeometry, wkt_regex, hex_regex
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from django.contrib.gis.geos.geometries import Point, LineString, LinearRing, Polygon, HAS_NUMPY
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from django.contrib.gis.geos.collections import GeometryCollection, MultiPoint, MultiLineString, MultiPolygon
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from django.contrib.gis.geos.error import GEOSException, GEOSIndexError
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from django.contrib.gis.geos.libgeos import geos_version, geos_version_info
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def fromfile(file_name):
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"""
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Given a string file name, returns a GEOSGeometry. The file may contain WKB,
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WKT, or HEX.
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"""
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fh = open(file_name, 'rb')
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buf = fh.read()
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fh.close()
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if wkt_regex.match(buf) or hex_regex.match(buf):
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return GEOSGeometry(buf)
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else:
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return GEOSGeometry(buffer(buf))
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def fromstr(wkt_or_hex, **kwargs):
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"Given a string value (wkt or hex), returns a GEOSGeometry object."
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return GEOSGeometry(wkt_or_hex, **kwargs)
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def hex_to_wkt(hex):
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"Converts HEXEWKB into WKT."
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return GEOSGeometry(hex).wkt
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def wkt_to_hex(wkt):
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"Converts WKT into HEXEWKB."
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return GEOSGeometry(wkt).hex
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def centroid(input):
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"Returns the centroid of the geometry (given in HEXEWKB)."
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return GEOSGeometry(input).centroid.wkt
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def area(input):
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"Returns the area of the geometry (given in HEXEWKB)."
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return GEOSGeometry(input).area
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