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django1/django/contrib/gis/gdal/geometries.py

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"""
The OGRGeometry is a wrapper for using the OGR Geometry class
(see http://www.gdal.org/ogr/classOGRGeometry.html). OGRGeometry
may be instantiated when reading geometries from OGR Data Sources
(e.g. SHP files), or when given OGC WKT (a string).
While the 'full' API is not present yet, the API is "pythonic" unlike
the traditional and "next-generation" OGR Python bindings. One major
advantage OGR Geometries have over their GEOS counterparts is support
for spatial reference systems and their transformation.
Example:
>>> from django.contrib.gis.gdal import OGRGeometry, OGRGeomType, SpatialReference
>>> wkt1, wkt2 = 'POINT(-90 30)', 'POLYGON((0 0, 5 0, 5 5, 0 5)'
>>> pnt = OGRGeometry(wkt1)
>>> print(pnt)
POINT (-90 30)
>>> mpnt = OGRGeometry(OGRGeomType('MultiPoint'), SpatialReference('WGS84'))
>>> mpnt.add(wkt1)
>>> mpnt.add(wkt1)
>>> print(mpnt)
MULTIPOINT (-90 30,-90 30)
>>> print(mpnt.srs.name)
WGS 84
>>> print(mpnt.srs.proj)
+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs
>>> mpnt.transform_to(SpatialReference('NAD27'))
>>> print(mpnt.proj)
+proj=longlat +ellps=clrk66 +datum=NAD27 +no_defs
>>> print(mpnt)
MULTIPOINT (-89.999930378602485 29.999797886557641,-89.999930378602485 29.999797886557641)
The OGRGeomType class is to make it easy to specify an OGR geometry type:
>>> from django.contrib.gis.gdal import OGRGeomType
>>> gt1 = OGRGeomType(3) # Using an integer for the type
>>> gt2 = OGRGeomType('Polygon') # Using a string
>>> gt3 = OGRGeomType('POLYGON') # It's case-insensitive
>>> print(gt1 == 3, gt1 == 'Polygon') # Equivalence works w/non-OGRGeomType objects
True True
"""
# Python library requisites.
import sys
from binascii import a2b_hex, b2a_hex
from ctypes import byref, string_at, c_char_p, c_double, c_ubyte, c_void_p
from django.contrib.gis import memoryview
# Getting GDAL prerequisites
from django.contrib.gis.gdal.base import GDALBase
from django.contrib.gis.gdal.envelope import Envelope, OGREnvelope
from django.contrib.gis.gdal.error import OGRException, OGRIndexError, SRSException
from django.contrib.gis.gdal.geomtype import OGRGeomType
from django.contrib.gis.gdal.libgdal import GDAL_VERSION
from django.contrib.gis.gdal.srs import SpatialReference, CoordTransform
# Getting the ctypes prototype functions that interface w/the GDAL C library.
from django.contrib.gis.gdal.prototypes import geom as capi, srs as srs_api
# For recognizing geometry input.
from django.contrib.gis.geometry.regex import hex_regex, wkt_regex, json_regex
from django.utils import six
from django.utils.six.moves import xrange
# For more information, see the OGR C API source code:
# http://www.gdal.org/ogr/ogr__api_8h.html
#
# The OGR_G_* routines are relevant here.
class OGRGeometry(GDALBase):
"Generally encapsulates an OGR geometry."
def __init__(self, geom_input, srs=None):
"Initializes Geometry on either WKT or an OGR pointer as input."
str_instance = isinstance(geom_input, six.string_types)
# If HEX, unpack input to a binary buffer.
if str_instance and hex_regex.match(geom_input):
geom_input = memoryview(a2b_hex(geom_input.upper().encode()))
str_instance = False
# Constructing the geometry,
if str_instance:
wkt_m = wkt_regex.match(geom_input)
json_m = json_regex.match(geom_input)
if wkt_m:
if wkt_m.group('srid'):
# If there's EWKT, set the SRS w/value of the SRID.
srs = int(wkt_m.group('srid'))
if wkt_m.group('type').upper() == 'LINEARRING':
# OGR_G_CreateFromWkt doesn't work with LINEARRING WKT.
# See http://trac.osgeo.org/gdal/ticket/1992.
g = capi.create_geom(OGRGeomType(wkt_m.group('type')).num)
capi.import_wkt(g, byref(c_char_p(wkt_m.group('wkt').encode())))
else:
g = capi.from_wkt(byref(c_char_p(wkt_m.group('wkt').encode())), None, byref(c_void_p()))
elif json_m:
g = capi.from_json(geom_input.encode())
else:
# Seeing if the input is a valid short-hand string
# (e.g., 'Point', 'POLYGON').
OGRGeomType(geom_input)
g = capi.create_geom(OGRGeomType(geom_input).num)
elif isinstance(geom_input, memoryview):
# WKB was passed in
g = capi.from_wkb(bytes(geom_input), None, byref(c_void_p()), len(geom_input))
elif isinstance(geom_input, OGRGeomType):
# OGRGeomType was passed in, an empty geometry will be created.
g = capi.create_geom(geom_input.num)
elif isinstance(geom_input, self.ptr_type):
# OGR pointer (c_void_p) was the input.
g = geom_input
else:
raise OGRException('Invalid input type for OGR Geometry construction: %s' % type(geom_input))
# Now checking the Geometry pointer before finishing initialization
# by setting the pointer for the object.
if not g:
raise OGRException('Cannot create OGR Geometry from input: %s' % str(geom_input))
self.ptr = g
# Assigning the SpatialReference object to the geometry, if valid.
if srs:
self.srs = srs
# Setting the class depending upon the OGR Geometry Type
self.__class__ = GEO_CLASSES[self.geom_type.num]
def __del__(self):
"Deletes this Geometry."
if self._ptr:
capi.destroy_geom(self._ptr)
# Pickle routines
def __getstate__(self):
srs = self.srs
if srs:
srs = srs.wkt
else:
srs = None
return bytes(self.wkb), srs
def __setstate__(self, state):
wkb, srs = state
ptr = capi.from_wkb(wkb, None, byref(c_void_p()), len(wkb))
if not ptr:
raise OGRException('Invalid OGRGeometry loaded from pickled state.')
self.ptr = ptr
self.srs = srs
@classmethod
def from_bbox(cls, bbox):
"Constructs a Polygon from a bounding box (4-tuple)."
x0, y0, x1, y1 = bbox
return OGRGeometry('POLYGON((%s %s, %s %s, %s %s, %s %s, %s %s))' % (
x0, y0, x0, y1, x1, y1, x1, y0, x0, y0))
### Geometry set-like operations ###
# g = g1 | g2
def __or__(self, other):
"Returns the union of the two geometries."
return self.union(other)
# g = g1 & g2
def __and__(self, other):
"Returns the intersection of this Geometry and the other."
return self.intersection(other)
# g = g1 - g2
def __sub__(self, other):
"Return the difference this Geometry and the other."
return self.difference(other)
# g = g1 ^ g2
def __xor__(self, other):
"Return the symmetric difference of this Geometry and the other."
return self.sym_difference(other)
def __eq__(self, other):
"Is this Geometry equal to the other?"
if isinstance(other, OGRGeometry):
return self.equals(other)
else:
return False
def __ne__(self, other):
"Tests for inequality."
return not (self == other)
def __str__(self):
"WKT is used for the string representation."
return self.wkt
#### Geometry Properties ####
@property
def dimension(self):
"Returns 0 for points, 1 for lines, and 2 for surfaces."
return capi.get_dims(self.ptr)
def _get_coord_dim(self):
"Returns the coordinate dimension of the Geometry."
return capi.get_coord_dim(self.ptr)
def _set_coord_dim(self, dim):
"Sets the coordinate dimension of this Geometry."
if not dim in (2, 3):
raise ValueError('Geometry dimension must be either 2 or 3')
capi.set_coord_dim(self.ptr, dim)
coord_dim = property(_get_coord_dim, _set_coord_dim)
@property
def geom_count(self):
"The number of elements in this Geometry."
return capi.get_geom_count(self.ptr)
@property
def point_count(self):
"Returns the number of Points in this Geometry."
return capi.get_point_count(self.ptr)
@property
def num_points(self):
"Alias for `point_count` (same name method in GEOS API.)"
return self.point_count
@property
def num_coords(self):
"Alais for `point_count`."
return self.point_count
@property
def geom_type(self):
"Returns the Type for this Geometry."
return OGRGeomType(capi.get_geom_type(self.ptr))
@property
def geom_name(self):
"Returns the Name of this Geometry."
return capi.get_geom_name(self.ptr)
@property
def area(self):
"Returns the area for a LinearRing, Polygon, or MultiPolygon; 0 otherwise."
return capi.get_area(self.ptr)
@property
def envelope(self):
"Returns the envelope for this Geometry."
# TODO: Fix Envelope() for Point geometries.
return Envelope(capi.get_envelope(self.ptr, byref(OGREnvelope())))
@property
def extent(self):
"Returns the envelope as a 4-tuple, instead of as an Envelope object."
return self.envelope.tuple
#### SpatialReference-related Properties ####
# The SRS property
def _get_srs(self):
"Returns the Spatial Reference for this Geometry."
try:
srs_ptr = capi.get_geom_srs(self.ptr)
return SpatialReference(srs_api.clone_srs(srs_ptr))
except SRSException:
return None
def _set_srs(self, srs):
"Sets the SpatialReference for this geometry."
# Do not have to clone the `SpatialReference` object pointer because
# when it is assigned to this `OGRGeometry` it's internal OGR
# reference count is incremented, and will likewise be released
# (decremented) when this geometry's destructor is called.
if isinstance(srs, SpatialReference):
srs_ptr = srs.ptr
elif isinstance(srs, six.integer_types + six.string_types):
sr = SpatialReference(srs)
srs_ptr = sr.ptr
else:
raise TypeError('Cannot assign spatial reference with object of type: %s' % type(srs))
capi.assign_srs(self.ptr, srs_ptr)
srs = property(_get_srs, _set_srs)
# The SRID property
def _get_srid(self):
srs = self.srs
if srs:
return srs.srid
return None
def _set_srid(self, srid):
if isinstance(srid, six.integer_types):
self.srs = srid
else:
raise TypeError('SRID must be set with an integer.')
srid = property(_get_srid, _set_srid)
#### Output Methods ####
@property
def geos(self):
"Returns a GEOSGeometry object from this OGRGeometry."
from django.contrib.gis.geos import GEOSGeometry
return GEOSGeometry(self.wkb, self.srid)
@property
def gml(self):
"Returns the GML representation of the Geometry."
return capi.to_gml(self.ptr)
@property
def hex(self):
"Returns the hexadecimal representation of the WKB (a string)."
return b2a_hex(self.wkb).upper()
@property
def json(self):
"""
Returns the GeoJSON representation of this Geometry.
"""
return capi.to_json(self.ptr)
geojson = json
@property
def kml(self):
"Returns the KML representation of the Geometry."
return capi.to_kml(self.ptr, None)
@property
def wkb_size(self):
"Returns the size of the WKB buffer."
return capi.get_wkbsize(self.ptr)
@property
def wkb(self):
"Returns the WKB representation of the Geometry."
if sys.byteorder == 'little':
byteorder = 1 # wkbNDR (from ogr_core.h)
else:
byteorder = 0 # wkbXDR
sz = self.wkb_size
# Creating the unsigned character buffer, and passing it in by reference.
buf = (c_ubyte * sz)()
capi.to_wkb(self.ptr, byteorder, byref(buf))
# Returning a buffer of the string at the pointer.
return memoryview(string_at(buf, sz))
@property
def wkt(self):
"Returns the WKT representation of the Geometry."
return capi.to_wkt(self.ptr, byref(c_char_p()))
@property
def ewkt(self):
"Returns the EWKT representation of the Geometry."
srs = self.srs
if srs and srs.srid:
return 'SRID=%s;%s' % (srs.srid, self.wkt)
else:
return self.wkt
#### Geometry Methods ####
def clone(self):
"Clones this OGR Geometry."
return OGRGeometry(capi.clone_geom(self.ptr), self.srs)
def close_rings(self):
"""
If there are any rings within this geometry that have not been
closed, this routine will do so by adding the starting point at the
end.
"""
# Closing the open rings.
capi.geom_close_rings(self.ptr)
def transform(self, coord_trans, clone=False):
"""
Transforms this geometry to a different spatial reference system.
May take a CoordTransform object, a SpatialReference object, string
WKT or PROJ.4, and/or an integer SRID. By default nothing is returned
and the geometry is transformed in-place. However, if the `clone`
keyword is set, then a transformed clone of this geometry will be
returned.
"""
if clone:
klone = self.clone()
klone.transform(coord_trans)
return klone
# Have to get the coordinate dimension of the original geometry
# so it can be used to reset the transformed geometry's dimension
# afterwards. This is done because of GDAL bug (in versions prior
# to 1.7) that turns geometries 3D after transformation, see:
# http://trac.osgeo.org/gdal/changeset/17792
if GDAL_VERSION < (1, 7):
orig_dim = self.coord_dim
# Depending on the input type, use the appropriate OGR routine
# to perform the transformation.
if isinstance(coord_trans, CoordTransform):
capi.geom_transform(self.ptr, coord_trans.ptr)
elif isinstance(coord_trans, SpatialReference):
capi.geom_transform_to(self.ptr, coord_trans.ptr)
elif isinstance(coord_trans, six.integer_types + six.string_types):
sr = SpatialReference(coord_trans)
capi.geom_transform_to(self.ptr, sr.ptr)
else:
raise TypeError('Transform only accepts CoordTransform, '
'SpatialReference, string, and integer objects.')
# Setting with original dimension, see comment above.
if GDAL_VERSION < (1, 7):
if isinstance(self, GeometryCollection):
# With geometry collections have to set dimension on
# each internal geometry reference, as the collection
# dimension isn't affected.
for i in xrange(len(self)):
internal_ptr = capi.get_geom_ref(self.ptr, i)
if orig_dim != capi.get_coord_dim(internal_ptr):
capi.set_coord_dim(internal_ptr, orig_dim)
else:
if self.coord_dim != orig_dim:
self.coord_dim = orig_dim
def transform_to(self, srs):
"For backwards-compatibility."
self.transform(srs)
#### Topology Methods ####
def _topology(self, func, other):
"""A generalized function for topology operations, takes a GDAL function and
the other geometry to perform the operation on."""
if not isinstance(other, OGRGeometry):
raise TypeError('Must use another OGRGeometry object for topology operations!')
# Returning the output of the given function with the other geometry's
# pointer.
return func(self.ptr, other.ptr)
def intersects(self, other):
"Returns True if this geometry intersects with the other."
return self._topology(capi.ogr_intersects, other)
def equals(self, other):
"Returns True if this geometry is equivalent to the other."
return self._topology(capi.ogr_equals, other)
def disjoint(self, other):
"Returns True if this geometry and the other are spatially disjoint."
return self._topology(capi.ogr_disjoint, other)
def touches(self, other):
"Returns True if this geometry touches the other."
return self._topology(capi.ogr_touches, other)
def crosses(self, other):
"Returns True if this geometry crosses the other."
return self._topology(capi.ogr_crosses, other)
def within(self, other):
"Returns True if this geometry is within the other."
return self._topology(capi.ogr_within, other)
def contains(self, other):
"Returns True if this geometry contains the other."
return self._topology(capi.ogr_contains, other)
def overlaps(self, other):
"Returns True if this geometry overlaps the other."
return self._topology(capi.ogr_overlaps, other)
#### Geometry-generation Methods ####
def _geomgen(self, gen_func, other=None):
"A helper routine for the OGR routines that generate geometries."
if isinstance(other, OGRGeometry):
return OGRGeometry(gen_func(self.ptr, other.ptr), self.srs)
else:
return OGRGeometry(gen_func(self.ptr), self.srs)
@property
def boundary(self):
"Returns the boundary of this geometry."
return self._geomgen(capi.get_boundary)
@property
def convex_hull(self):
"""
Returns the smallest convex Polygon that contains all the points in
this Geometry.
"""
return self._geomgen(capi.geom_convex_hull)
def difference(self, other):
"""
Returns a new geometry consisting of the region which is the difference
of this geometry and the other.
"""
return self._geomgen(capi.geom_diff, other)
def intersection(self, other):
"""
Returns a new geometry consisting of the region of intersection of this
geometry and the other.
"""
return self._geomgen(capi.geom_intersection, other)
def sym_difference(self, other):
"""
Returns a new geometry which is the symmetric difference of this
geometry and the other.
"""
return self._geomgen(capi.geom_sym_diff, other)
def union(self, other):
"""
Returns a new geometry consisting of the region which is the union of
this geometry and the other.
"""
return self._geomgen(capi.geom_union, other)
# The subclasses for OGR Geometry.
class Point(OGRGeometry):
@property
def x(self):
"Returns the X coordinate for this Point."
return capi.getx(self.ptr, 0)
@property
def y(self):
"Returns the Y coordinate for this Point."
return capi.gety(self.ptr, 0)
@property
def z(self):
"Returns the Z coordinate for this Point."
if self.coord_dim == 3:
return capi.getz(self.ptr, 0)
@property
def tuple(self):
"Returns the tuple of this point."
if self.coord_dim == 2:
return (self.x, self.y)
elif self.coord_dim == 3:
return (self.x, self.y, self.z)
coords = tuple
class LineString(OGRGeometry):
def __getitem__(self, index):
"Returns the Point at the given index."
if index >= 0 and index < self.point_count:
x, y, z = c_double(), c_double(), c_double()
capi.get_point(self.ptr, index, byref(x), byref(y), byref(z))
dim = self.coord_dim
if dim == 1:
return (x.value,)
elif dim == 2:
return (x.value, y.value)
elif dim == 3:
return (x.value, y.value, z.value)
else:
raise OGRIndexError('index out of range: %s' % str(index))
def __iter__(self):
"Iterates over each point in the LineString."
for i in xrange(self.point_count):
yield self[i]
def __len__(self):
"The length returns the number of points in the LineString."
return self.point_count
@property
def tuple(self):
"Returns the tuple representation of this LineString."
return tuple(self[i] for i in xrange(len(self)))
coords = tuple
def _listarr(self, func):
"""
Internal routine that returns a sequence (list) corresponding with
the given function.
"""
return [func(self.ptr, i) for i in xrange(len(self))]
@property
def x(self):
"Returns the X coordinates in a list."
return self._listarr(capi.getx)
@property
def y(self):
"Returns the Y coordinates in a list."
return self._listarr(capi.gety)
@property
def z(self):
"Returns the Z coordinates in a list."
if self.coord_dim == 3:
return self._listarr(capi.getz)
# LinearRings are used in Polygons.
class LinearRing(LineString):
pass
class Polygon(OGRGeometry):
def __len__(self):
"The number of interior rings in this Polygon."
return self.geom_count
def __iter__(self):
"Iterates through each ring in the Polygon."
for i in xrange(self.geom_count):
yield self[i]
def __getitem__(self, index):
"Gets the ring at the specified index."
if index < 0 or index >= self.geom_count:
raise OGRIndexError('index out of range: %s' % index)
else:
return OGRGeometry(capi.clone_geom(capi.get_geom_ref(self.ptr, index)), self.srs)
# Polygon Properties
@property
def shell(self):
"Returns the shell of this Polygon."
return self[0] # First ring is the shell
exterior_ring = shell
@property
def tuple(self):
"Returns a tuple of LinearRing coordinate tuples."
return tuple(self[i].tuple for i in xrange(self.geom_count))
coords = tuple
@property
def point_count(self):
"The number of Points in this Polygon."
# Summing up the number of points in each ring of the Polygon.
return sum(self[i].point_count for i in xrange(self.geom_count))
@property
def centroid(self):
"Returns the centroid (a Point) of this Polygon."
# The centroid is a Point, create a geometry for this.
p = OGRGeometry(OGRGeomType('Point'))
capi.get_centroid(self.ptr, p.ptr)
return p
# Geometry Collection base class.
class GeometryCollection(OGRGeometry):
"The Geometry Collection class."
def __getitem__(self, index):
"Gets the Geometry at the specified index."
if index < 0 or index >= self.geom_count:
raise OGRIndexError('index out of range: %s' % index)
else:
return OGRGeometry(capi.clone_geom(capi.get_geom_ref(self.ptr, index)), self.srs)
def __iter__(self):
"Iterates over each Geometry."
for i in xrange(self.geom_count):
yield self[i]
def __len__(self):
"The number of geometries in this Geometry Collection."
return self.geom_count
def add(self, geom):
"Add the geometry to this Geometry Collection."
if isinstance(geom, OGRGeometry):
if isinstance(geom, self.__class__):
for g in geom:
capi.add_geom(self.ptr, g.ptr)
else:
capi.add_geom(self.ptr, geom.ptr)
elif isinstance(geom, six.string_types):
tmp = OGRGeometry(geom)
capi.add_geom(self.ptr, tmp.ptr)
else:
raise OGRException('Must add an OGRGeometry.')
@property
def point_count(self):
"The number of Points in this Geometry Collection."
# Summing up the number of points in each geometry in this collection
return sum(self[i].point_count for i in xrange(self.geom_count))
@property
def tuple(self):
"Returns a tuple representation of this Geometry Collection."
return tuple(self[i].tuple for i in xrange(self.geom_count))
coords = tuple
# Multiple Geometry types.
class MultiPoint(GeometryCollection):
pass
class MultiLineString(GeometryCollection):
pass
class MultiPolygon(GeometryCollection):
pass
# Class mapping dictionary (using the OGRwkbGeometryType as the key)
GEO_CLASSES = {1: Point,
2: LineString,
3: Polygon,
4: MultiPoint,
5: MultiLineString,
6: MultiPolygon,
7: GeometryCollection,
101: LinearRing,
1 + OGRGeomType.wkb25bit: Point,
2 + OGRGeomType.wkb25bit: LineString,
3 + OGRGeomType.wkb25bit: Polygon,
4 + OGRGeomType.wkb25bit: MultiPoint,
5 + OGRGeomType.wkb25bit: MultiLineString,
6 + OGRGeomType.wkb25bit: MultiPolygon,
7 + OGRGeomType.wkb25bit: GeometryCollection,
}
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