Apa itu GEOS?¶

GEOS stands for Geometry Engine - Open Source, and is a C++ library, ported from the Java Topology Suite. GEOS implements the OpenGIS Simple Features for SQL spatial predicate functions and spatial operators. GEOS, now an OSGeo project, was initially developed and maintained by Refractions Research of Victoria, Canada.

Fitur¶

GeoDjango menerapkan pembungkus Python tingkat-tinggi untuk pustaka GEOS, fitur-fiturnya termasuk:

• A BSD-licensed interface to the GEOS geometry routines, implemented purely in Python using ctypes.
• Loosely-coupled to GeoDjango. For example, GEOSGeometry objects may be used outside of a Django project/application. In other words, no need to have DJANGO_SETTINGS_MODULE set or use a database, etc.
• Berubah-ubah: obyek GEOSGeometry mungkin dirubah.
• Cross-platform and tested; compatible with Windows, Linux, Solaris, and macOS platforms.

Membuat Geometri¶

GEOSGeometry objects may be created in a few ways. The first is to simply instantiate the object on some spatial input -- the following are examples of creating the same geometry from WKT, HEX, WKB, and GeoJSON:

>>> from django.contrib.gis.geos import GEOSGeometry
>>> pnt = GEOSGeometry('POINT(5 23)') # WKT
>>> pnt = GEOSGeometry('010100000000000000000014400000000000003740') # HEX
>>> pnt = GEOSGeometry(buffer('\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x14@\x00\x00\x00\x00\x00\x007@'))
>>> pnt = GEOSGeometry('{ "type": "Point", "coordinates": [ 5.000000, 23.000000 ] }') # GeoJSON

Another option is to use the constructor for the specific geometry type that you wish to create. For example, a Point object may be created by passing in the X and Y coordinates into its constructor:

>>> from django.contrib.gis.geos import Point
>>> pnt = Point(5, 23)

All these constructors take the keyword argument srid. For example:

>>> from django.contrib.gis.geos import GEOSGeometry, LineString, Point
>>> print(GEOSGeometry('POINT (0 0)', srid=4326))
SRID=4326;POINT (0 0)
>>> print(LineString((0, 0), (1, 1), srid=4326))
SRID=4326;LINESTRING (0 0, 1 1)
>>> print(Point(0, 0, srid=32140))
SRID=32140;POINT (0 0)

Finally, there is the fromfile() factory method which returns a GEOSGeometry object from a file:

>>> from django.contrib.gis.geos import fromfile
>>> pnt = fromfile('/path/to/pnt.wkt')
>>> pnt = fromfile(open('/path/to/pnt.wkt'))

Geometries are Pythonic¶

GEOSGeometry objects are 'Pythonic', in other words components may be accessed, modified, and iterated over using standard Python conventions. For example, you can iterate over the coordinates in a Point:

>>> pnt = Point(5, 23)
>>> [coord for coord in pnt]
[5.0, 23.0]

With any geometry object, the GEOSGeometry.coords property may be used to get the geometry coordinates as a Python tuple:

>>> pnt.coords
(5.0, 23.0)

You can get/set geometry components using standard Python indexing techniques. However, what is returned depends on the geometry type of the object. For example, indexing on a LineString returns a coordinate tuple:

>>> from django.contrib.gis.geos import LineString
>>> line = LineString((0, 0), (0, 50), (50, 50), (50, 0), (0, 0))
>>> line[0]
(0.0, 0.0)
>>> line[-2]
(50.0, 0.0)

Whereas indexing on a Polygon will return the ring (a LinearRing object) corresponding to the index:

>>> from django.contrib.gis.geos import Polygon
>>> poly = Polygon( ((0.0, 0.0), (0.0, 50.0), (50.0, 50.0), (50.0, 0.0), (0.0, 0.0)) )
>>> poly[0]
<LinearRing object at 0x1044395b0>
>>> poly[0][-2] # second-to-last coordinate of external ring
(50.0, 0.0)

In addition, coordinates/components of the geometry may added or modified, just like a Python list:

>>> line[0] = (1.0, 1.0)
>>> line.pop()
(0.0, 0.0)
>>> line.append((1.0, 1.0))
>>> line.coords
((1.0, 1.0), (0.0, 50.0), (50.0, 50.0), (50.0, 0.0), (1.0, 1.0))

Geometries support set-like operators:

>>> from django.contrib.gis.geos import LineString
>>> ls1 = LineString((0, 0), (2, 2))
>>> ls2 = LineString((1, 1), (3, 3))
>>> print(ls1 | ls2)  # equivalent to `ls1.union(ls2)`
MULTILINESTRING ((0 0, 1 1), (1 1, 2 2), (2 2, 3 3))
>>> print(ls1 & ls2)  # equivalent to `ls1.intersection(ls2)`
LINESTRING (1 1, 2 2)
>>> print(ls1 - ls2)  # equivalent to `ls1.difference(ls2)`
LINESTRING(0 0, 1 1)
>>> print(ls1 ^ ls2)  # equivalent to `ls1.sym_difference(ls2)`
MULTILINESTRING ((0 0, 1 1), (2 2, 3 3))

>>> from django.contrib.gis.geos import LineString
>>> ls1 = LineString((0, 0), (1, 1))
>>> ls2 = LineString((1, 1), (0, 0))
>>> ls3 = LineString((1, 1), (0, 0), srid=4326)
>>> ls1.equals(ls2)
True
>>> ls1 == ls2
False
>>> ls3 == ls2  # different SRIDs
False

GEOSGeometry¶

class GEOSGeometry(geo_input, srid=None)¶

Parameter:	geo_input -- Geometry input value (string or buffer) srid (int) -- spatial reference identifier

This is the base class for all GEOS geometry objects. It initializes on the given geo_input argument, and then assumes the proper geometry subclass (e.g., GEOSGeometry('POINT(1 1)') will create a Point object).

The srid parameter, if given, is set as the SRID of the created geometry if geo_input doesn't have an SRID. If different SRIDs are provided through the geo_input and srid parameters, ValueError is raised:

>>> from django.contrib.gis.geos import GEOSGeometry
>>> GEOSGeometry('POINT EMPTY', srid=4326).ewkt
'SRID=4326;POINT EMPTY'
>>> GEOSGeometry('SRID=4326;POINT EMPTY', srid=4326).ewkt
'SRID=4326;POINT EMPTY'
>>> GEOSGeometry('SRID=1;POINT EMPTY', srid=4326)
Traceback (most recent call last):
...
ValueError: Input geometry already has SRID: 1.

The following input formats, along with their corresponding Python types, are accepted:

For the GeoJSON format, the SRID is set based on the crs member. If crs isn't provided, the SRID defaults to 4326.

classmethod GEOSGeometry.from_gml(gml_string)¶

New in Django 1.11.

Constructs a GEOSGeometry from the given GML string.

Point¶

class Point(x=None, y=None, z=None, srid=None)¶

Point objects are instantiated using arguments that represent the component coordinates of the point or with a single sequence coordinates. For example, the following are equivalent:

>>> pnt = Point(5, 23)
>>> pnt = Point([5, 23])

Empty Point objects may be instantiated by passing no arguments or an empty sequence. The following are equivalent:

>>> pnt = Point()
>>> pnt = Point([])

LineString¶

class LineString(*args, **kwargs)¶

LineString objects are instantiated using arguments that are either a sequence of coordinates or Point objects. For example, the following are equivalent:

>>> ls = LineString((0, 0), (1, 1))
>>> ls = LineString(Point(0, 0), Point(1, 1))

In addition, LineString objects may also be created by passing in a single sequence of coordinate or Point objects:

>>> ls = LineString( ((0, 0), (1, 1)) )
>>> ls = LineString( [Point(0, 0), Point(1, 1)] )

Empty LineString objects may be instantiated by passing no arguments or an empty sequence. The following are equivalent:

>>> ls = LineString()
>>> ls = LineString([])

closed¶

Mengembalikan apakah atau tidak LineString ini ditutup.

LinearRing¶

class LinearRing(*args, **kwargs)¶

LinearRing objects are constructed in the exact same way as LineString objects, however the coordinates must be closed, in other words, the first coordinates must be the same as the last coordinates. For example:

>>> ls = LinearRing((0, 0), (0, 1), (1, 1), (0, 0))

Perhatikan bahwa (0, 0) adalah kordinat pertama dan terakhir -- jika mereka tidak setara, sebuah kesalahan akan dimunculkan.

Polygon¶

class Polygon(*args, **kwargs)¶

Polygon objects may be instantiated by passing in parameters that represent the rings of the polygon. The parameters must either be LinearRing instances, or a sequence that may be used to construct a LinearRing:

>>> ext_coords = ((0, 0), (0, 1), (1, 1), (1, 0), (0, 0))
>>> int_coords = ((0.4, 0.4), (0.4, 0.6), (0.6, 0.6), (0.6, 0.4), (0.4, 0.4))
>>> poly = Polygon(ext_coords, int_coords)
>>> poly = Polygon(LinearRing(ext_coords), LinearRing(int_coords))

classmethod from_bbox(bbox)¶

Mengembalikan sebuah obyek poligon dari kotak-dikelilingi diberikan, 4-tuple meliputi (xmin, ymin, xmax, ymax).

num_interior_rings¶

Mengembalikan sejumlah lingkaran interior di geometri ini.

>>> if poly_1.area > poly_2.area:
>>>     pass

MultiPoint¶

class MultiPoint(*args, **kwargs)¶

MultiPoint objects may be instantiated by passing in Point objects as arguments, or a single sequence of Point objects:

>>> mp = MultiPoint(Point(0, 0), Point(1, 1))
>>> mp = MultiPoint( (Point(0, 0), Point(1, 1)) )

MultiLineString¶

class MultiLineString(*args, **kwargs)¶

MultiLineString objects may be instantiated by passing in LineString objects as arguments, or a single sequence of LineString objects:

>>> ls1 = LineString((0, 0), (1, 1))
>>> ls2 = LineString((2, 2), (3, 3))
>>> mls = MultiLineString(ls1, ls2)
>>> mls = MultiLineString([ls1, ls2])

merged¶

Mengembalikan sebuah LineString mewakili baris menggabungkan semua komponen di MultiLineString ini.

closed¶

Mengembalikan True jika dan hanya jika semua unsur ditutup. Membutuhkan GEOS 3.5.

MultiPolygon¶

class MultiPolygon(*args, **kwargs)¶

MultiPolygon objects may be instantiated by passing Polygon objects as arguments, or a single sequence of Polygon objects:

>>> p1 = Polygon( ((0, 0), (0, 1), (1, 1), (0, 0)) )
>>> p2 = Polygon( ((1, 1), (1, 2), (2, 2), (1, 1)) )
>>> mp = MultiPolygon(p1, p2)
>>> mp = MultiPolygon([p1, p2])

GeometryCollection¶

class GeometryCollection(*args, **kwargs)¶

GeometryCollection objects may be instantiated by passing in other GEOSGeometry as arguments, or a single sequence of GEOSGeometry objects:

>>> poly = Polygon( ((0, 0), (0, 1), (1, 1), (0, 0)) )
>>> gc = GeometryCollection(Point(0, 0), MultiPoint(Point(0, 0), Point(1, 1)), poly)
>>> gc = GeometryCollection((Point(0, 0), MultiPoint(Point(0, 0), Point(1, 1)), poly))

PreparedGeometry¶

class PreparedGeometry¶

Semua metode pada PreparedGeometry mengambil sebuah argumen other, yang harus berupa instance GEOSGeometry.

contains(other)¶

contains_properly(other)¶

covers(other)¶

crosses(other)¶

disjoint(other)¶

intersects(other)¶

overlaps(other)¶

touches(other)¶

within(other)¶

Obyek Pembaca¶

The reader I/O classes simply return a GEOSGeometry instance from the WKB and/or WKT input given to their read(geom) method.

class WKBReader¶

Contoh:

>>> from django.contrib.gis.geos import WKBReader
>>> wkb_r = WKBReader()
>>> wkb_r.read('0101000000000000000000F03F000000000000F03F')
<Point object at 0x103a88910>

class WKTReader¶

Contoh:

>>> from django.contrib.gis.geos import WKTReader
>>> wkt_r = WKTReader()
>>> wkt_r.read('POINT(1 1)')
<Point object at 0x103a88b50>

Obyek Penulis¶

All writer objects have a write(geom) method that returns either the WKB or WKT of the given geometry. In addition, WKBWriter objects also have properties that may be used to change the byte order, and or include the SRID value (in other words, EWKB).

class WKBWriter(dim=2)¶

WKBWriter provides the most control over its output. By default it returns OGC-compliant WKB when its write method is called. However, it has properties that allow for the creation of EWKB, a superset of the WKB standard that includes additional information. See the WKBWriter.outdim documentation for more details about the dim argument.

write(geom)¶

Returns the WKB of the given geometry as a Python buffer object. Example:

>>> from django.contrib.gis.geos import Point, WKBWriter
>>> pnt = Point(1, 1)
>>> wkb_w = WKBWriter()
>>> wkb_w.write(pnt)
<read-only buffer for 0x103a898f0, size -1, offset 0 at 0x103a89930>

write_hex(geom)¶

Mengembalikan WKB dari geometri di heksadesimal. Contoh:

>>> from django.contrib.gis.geos import Point, WKBWriter
>>> pnt = Point(1, 1)
>>> wkb_w = WKBWriter()
>>> wkb_w.write_hex(pnt)
'0101000000000000000000F03F000000000000F03F'

byteorder¶

This property may be set to change the byte-order of the geometry representation.

Nilai Byteorder	Deskripsi
0	Big Endian (sebagai contoh, cocok dengan sistem RISC)
1	Little Endian (sebagai contoh, cocok dengan sistem x86)

Contoh:

>>> from django.contrib.gis.geos import Point, WKBWriter
>>> wkb_w = WKBWriter()
>>> pnt = Point(1, 1)
>>> wkb_w.write_hex(pnt)
'0101000000000000000000F03F000000000000F03F'
>>> wkb_w.byteorder = 0
'00000000013FF00000000000003FF0000000000000'

outdim¶

This property may be set to change the output dimension of the geometry representation. In other words, if you have a 3D geometry then set to 3 so that the Z value is included in the WKB.

Nilai Outdim	Deskripsi
2	Awalan, keluaran 2D WKB.
3	Keluaran 3D WKB.

Contoh:

>>> from django.contrib.gis.geos import Point, WKBWriter
>>> wkb_w = WKBWriter()
>>> wkb_w.outdim
2
>>> pnt = Point(1, 1, 1)
>>> wkb_w.write_hex(pnt) # By default, no Z value included:
'0101000000000000000000F03F000000000000F03F'
>>> wkb_w.outdim = 3 # Tell writer to include Z values
>>> wkb_w.write_hex(pnt)
'0101000080000000000000F03F000000000000F03F000000000000F03F'

srid¶

Set this property with a boolean to indicate whether the SRID of the geometry should be included with the WKB representation. Example:

>>> from django.contrib.gis.geos import Point, WKBWriter
>>> wkb_w = WKBWriter()
>>> pnt = Point(1, 1, srid=4326)
>>> wkb_w.write_hex(pnt) # By default, no SRID included:
'0101000000000000000000F03F000000000000F03F'
>>> wkb_w.srid = True # Tell writer to include SRID
>>> wkb_w.write_hex(pnt)
'0101000020E6100000000000000000F03F000000000000F03F'

class WKTWriter(dim=2, trim=False, precision=None)¶

This class allows outputting the WKT representation of a geometry. See the WKBWriter.outdim, trim, and precision attributes for details about the constructor arguments.

write(geom)¶

Mengembalikan WKT dari geometri diberikan. Contoh:

>>> from django.contrib.gis.geos import Point, WKTWriter
>>> pnt = Point(1, 1)
>>> wkt_w = WKTWriter()
>>> wkt_w.write(pnt)
'POINT (1.0000000000000000 1.0000000000000000)'

outdim¶

Lihat WKBWriter.outdim.

trim¶

Sifat ini digunakan untuk mengadakan atau meniadakan memangkas dari desimal yang tidak diperlukan.

>>> from django.contrib.gis.geos import Point, WKTWriter
>>> pnt = Point(1, 1)
>>> wkt_w = WKTWriter()
>>> wkt_w.trim
False
>>> wkt_w.write(pnt)
'POINT (1.0000000000000000 1.0000000000000000)'
>>> wkt_w.trim = True
>>> wkt_w.write(pnt)
'POINT (1 1)'

precision¶

Sifat ini mengendalikan ketelitian pembulatan dari kordinat; jika disetel menjadi None pembulatan adalah ditiadakan.

>>> from django.contrib.gis.geos import Point, WKTWriter
>>> pnt = Point(1.44, 1.66)
>>> wkt_w = WKTWriter()
>>> print(wkt_w.precision)
None
>>> wkt_w.write(pnt)
'POINT (1.4399999999999999 1.6599999999999999)'
>>> wkt_w.precision = 0
>>> wkt_w.write(pnt)
'POINT (1 2)'
>>> wkt_w.precision = 1
>>> wkt_w.write(pnt)
'POINT (1.4 1.7)'

Catatan kaki

GEOS_LIBRARY_PATH¶

Sebuah string menentukan tempat dari pustaka C GEOS. Khususnya, pengaturan ini hanya digunakan jika pustaka C GEOS adalah di tempat bukan-standar (sebagai contoh, /home/bob/lib/libgeos_c.so).