1 """

     2  This module houses the Geometry Collection objects:

     3  GeometryCollection, MultiPoint, MultiLineString, and MultiPolygon

     4 """

     5 from ctypes import c_int, c_uint, byref

     6 from django.contrib.gis.geos.error import GEOSException, GEOSIndexError

     7 from django.contrib.gis.geos.geometry import GEOSGeometry

     8 from django.contrib.gis.geos.libgeos import get_pointer_arr, GEOM_PTR, GEOS_PREPARE

     9 from django.contrib.gis.geos.linestring import LineString, LinearRing

    10 from django.contrib.gis.geos.point import Point

    11 from django.contrib.gis.geos.polygon import Polygon

    12 from django.contrib.gis.geos import prototypes as capi

    13 

    14 class GeometryCollection(GEOSGeometry):

    15     _typeid = 7

    16 

    17     def __init__(self, *args, **kwargs):

    18         "Initializes a Geometry Collection from a sequence of Geometry objects."

    19 

    20         # Checking the arguments

    21         if not args:

    22             raise TypeError, 'Must provide at least one Geometry to initialize %s.' % self.__class__.__name__

    23 

    24         if len(args) == 1:

    25             # If only one geometry provided or a list of geometries is provided

    26             #  in the first argument.

    27             if isinstance(args[0], (tuple, list)):

    28                 init_geoms = args[0]

    29             else:

    30                 init_geoms = args

    31         else:

    32             init_geoms = args

    33 

    34         # Ensuring that only the permitted geometries are allowed in this collection

    35         # this is moved to list mixin super class

    36         self._check_allowed(init_geoms)

    37 

    38         # Creating the geometry pointer array.

    39         collection = self._create_collection(len(init_geoms), iter(init_geoms))

    40         super(GeometryCollection, self).__init__(collection, **kwargs)

    41 

    42     def __iter__(self):

    43         "Iterates over each Geometry in the Collection."

    44         for i in xrange(len(self)):

    45             yield self[i]

    46 

    47     def __len__(self):

    48         "Returns the number of geometries in this Collection."

    49         return self.num_geom

    50 

    51     ### Methods for compatibility with ListMixin ###

    52     def _create_collection(self, length, items):

    53         # Creating the geometry pointer array.

    54         geoms = get_pointer_arr(length)

    55         for i, g in enumerate(items):

    56             # this is a little sloppy, but makes life easier

    57             # allow GEOSGeometry types (python wrappers) or pointer types

    58             geoms[i] = capi.geom_clone(getattr(g, 'ptr', g))

    59 

    60         return capi.create_collection(c_int(self._typeid), byref(geoms), c_uint(length))

    61 

    62     def _get_single_internal(self, index):

    63         return capi.get_geomn(self.ptr, index)

    64 

    65     def _get_single_external(self, index):

    66         "Returns the Geometry from this Collection at the given index (0-based)."

    67         # Checking the index and returning the corresponding GEOS geometry.

    68         return GEOSGeometry(capi.geom_clone(self._get_single_internal(index)), srid=self.srid)

    69 

    70     def _set_list(self, length, items):

    71         "Create a new collection, and destroy the contents of the previous pointer."

    72         prev_ptr = self.ptr

    73         srid = self.srid

    74         self.ptr = self._create_collection(length, items)

    75         if srid: self.srid = srid

    76         capi.destroy_geom(prev_ptr)

    77 

    78     _set_single = GEOSGeometry._set_single_rebuild

    79     _assign_extended_slice = GEOSGeometry._assign_extended_slice_rebuild

    80 

    81     @property

    82     def kml(self):

    83         "Returns the KML for this Geometry Collection."

    84         return '<MultiGeometry>%s</MultiGeometry>' % ''.join([g.kml for g in self])

    85 

    86     @property

    87     def tuple(self):

    88         "Returns a tuple of all the coordinates in this Geometry Collection"

    89         return tuple([g.tuple for g in self])

    90     coords = tuple

    91 

    92 # MultiPoint, MultiLineString, and MultiPolygon class definitions.

    93 class MultiPoint(GeometryCollection):

    94     _allowed = Point

    95     _typeid = 4

    96 

    97 class MultiLineString(GeometryCollection):

    98     _allowed = (LineString, LinearRing)

    99     _typeid = 5

   100 

   101     @property

   102     def merged(self):

   103         """ 

   104         Returns a LineString representing the line merge of this 

   105         MultiLineString.

   106         """ 

   107         return self._topology(capi.geos_linemerge(self.ptr))         

   108 

   109 class MultiPolygon(GeometryCollection):

   110     _allowed = Polygon

   111     _typeid = 6

   112 

   113     @property

   114     def cascaded_union(self):

   115         "Returns a cascaded union of this MultiPolygon."

   116         if GEOS_PREPARE:

   117             return GEOSGeometry(capi.geos_cascaded_union(self.ptr), self.srid)

   118         else:

   119             raise GEOSException('The cascaded union operation requires GEOS 3.1+.')

   120 

   121 # Setting the allowed types here since GeometryCollection is defined before

   122 # its subclasses.

   123 GeometryCollection._allowed = (Point, LineString, LinearRing, Polygon, MultiPoint, MultiLineString, MultiPolygon)