python Shapely使用指南详解

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参考python Shapely使用指南详解 – 云+社区 – 腾讯云

Shapely是一个Python库，用于操作和分析笛卡尔坐标系中的几何对象。

引入包

from shapely.geometry import Point


from shapely.geometry import LineString

共有的变量和方法

object.area

　　Returns the area (float) of the object.

object.bounds

　　返回对象的（minx,miny,maxx,maxy）元组（float类型）

object.length

　　返回对象的长度

object.geom_type

　　返回对象类型

object.distance(other)

　　返回本对象和另一个对象的距离

object.representative_point()

　　Returns a cheaply computed point that is guaranteed to be within the geometric object.

>>> from shapely.geometry import Point

>>> print Point(0,0).distance(Point(0,1))

1.0

>>> from shapely.geometry import LineString

>>> line = LineString([(0,0), (1,1), (1,2)])

>>> line.area

0.0

>>> line.bounds

(0.0, 0.0, 1.0, 2.0)

>>> line.length

2.414213562373095

>>> line.geom_type

'LineString'

Point

class Point(coordinates)

三种赋值方式

>>> point = Point(0,0)

>>> point_2 = Point((0,0))

>>> point_3 = Point(point)

一个点对象有area和长度都为0

>>> point.area

0.0

>>> point.length

0.0

坐标可以通过coords或x、y、z得到

>>> p = Point(2,3)

>>> p.coords

<shapely.coords.CoordinateSequence object at 0x7ffbc3d60dd0>


>>> list(p.coords)

[(2.0, 3.0)]

>>> p.x

2.0

>>> p.y

3.0

coords可以被切片

>>> p.coords[:]

[(2.0, 3.0)]

LineStrings

LineStrings构造函数传入参数是2个或多个点序列

一个LineStrings对象area为0，长度非0

>>> line = LineString([(0,0), (0,1), (1,2)])

>>> line.area

0.0

>>> line.length

2.414213562373095

获得坐标

>>> line.coords[:]

[(0.0, 0.0), (0.0, 1.0), (1.0, 2.0)]

 >>> list(line.coords)

 [(0.0, 0.0), (0.0, 1.0), (1.0, 2.0)]

LineString依然可以接受一个同类型对象

>>> line2 = LineString(line)

>>> line2.coords[:]

[(0.0, 0.0), (0.0, 1.0), (1.0, 2.0)]

常见格式转换

>>> Point(1,1).wkt

'POINT (1 1)'

>>> Point(1,1).wkb

'\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\xf0?\x00\x00\x00\x00\x00\x00\xf0?'

>>> Point(1,1).wkb.encode('hex')

'0101000000000000000000f03f000000000000f03f'

>>>

>>> Point(1,1).wkb.encode('hex')

'0101000000000000000000f03f000000000000f03f'

两者都有loads和dumps方法

对于wkt

>>> from shapely.wkt import dumps, loads

>>> s = dumps(Point(1,2))

>>> s

'POINT (1.0000000000000000 2.0000000000000000)'

>>> ss = loads(s)

>>> ss

<shapely.geometry.point.Point object at 0x7ffbc3d783d0>

>>> ss.coords[:]

[(1.0, 2.0)]

对于wkb

>>> from shapely.wkb import dumps, loads

>>> s = dumps(Point(1,2), hex=True)

>>> s

'0101000000000000000000F03F0000000000000040'

>>> ss = loads(s, hex=True)

>>> ss

<shapely.geometry.point.Point object at 0x7ffbc3d78790>

>>> ss.coords

<shapely.coords.CoordinateSequence object at 0x7ffbc3d783d0>

>>> ss.coords[:]

[(1.0, 2.0)]