GIS算法：7_python拓扑套件shapely

标签： GIS算法

可用于GIS数据处理与空间计算的Python包有GDAL和shapely。

相对来说，GDAL功能更全面，还可以用于数据转换、瓦片地图发布、栅格影像分析等，shapely只能进行基本的数据处理和空间计算。

但大多数情况下shapely就完全够用了。

GDAL的官网：https://gdal.org/

Shapely的中文文档：https://www.osgeo.cn/shapely/

本例只讲shapely的用法。

可以通过cmd安装shapely，打开cmd，输入python，回车，查看python的版本号。

去下载shapely安装程序，https://www.lfd.uci.edu/~gohlke/pythonlibs/#shapely

根据python版本和电脑位数，选了Shapely-1.6.4.post2-cp37-cp37m-win32.whl下载。

安装的时候，打开cmd，运行语句：pip install D:\gismap\软件\Shapely-1.6.4.post2-cp37-cp37m-win32.whl，输入，回车。其中D:\gismap\软件\是放安装包的路径。

如果提示，

提示要升级pip，写啥就敲啥。python -m pip install --upgrade pip

升级完了，接着运行上一个语句，把shapely安装了。

构建RTree：生成50×50个点，根据这些点生成缓冲1.0的圆，用这些圆构建RTree，在RTree中查点[1,1]落在哪些圆里。

from shapely.geometry import Point
from shapely.strtree import STRtree
polygons=[]
for i in range(0,50):
    for j in range(0,50):
        polygon=Point([i,j]).buffer(1.0)
        polygon.__setattr__('id',str(i)+str(j))
        polygons.append(polygon)
tree=STRtree(polygons)
result=tree.query(Point(1,1))
for r in result:
    print(r.__getattribute__('id'))

线裁切面：如图所示，用红色线去裁切蓝色面，结果会生成3个面。

from shapely import wkt
from shapely.ops import polygonize
polygon=wkt.loads('POLYGON ((220 350, 400 440, 635 249, 380 80, 174 164, 179 265, 220 350))')
polyline=wkt.loads('LINESTRING (570 400, 392 315, 299 215, 430 140, 530 240, 450 360, 460 480)')
boundary=polygon.boundary
polyline=polyline.union(boundary)
lineList = []
for i in range(0,len(polyline.geoms)):
    lineList.append(polyline.geoms[i])
clipPolygon=polygonize(lineList)
buffer=polygon.buffer(1)
for c in clipPolygon:
    if buffer.contains(c):
        print(c)

将裁切线换成LINESTRING (320 330, 500 280, 400 150, 290 200, 400 360)，结果如下：

结果可以在JTS TestBuilder中查验。

在控制台input的文本框中输入wkt文本，点击load geometrys，就可以在面板中展示图形。

Shapely常用函数列表：

Geometric Objects
object.area	Returns the area (float) of the object.
object.bounds	Returns a (minx, miny, maxx, maxy) tuple (float values) that bounds the object.
object.length	Returns the length (float) of the object.
object.geom_type	Returns a string specifying the Geometry Type	类型
object.distance(other)	Returns the minimum distance (float) to the othergeometric object.
object.representative_point()	Returns a cheaply computed point that is guaranteed to be within the geometric object.	返回几何图形内的标志点，不是图心或质心，因为凹多边形的图心或质心可能在几何图形外

Unary Predicates		一元谓词关系判断
object.has_z	Returns True if the feature has not only x and y, but also z coordinates for 3D (or so-called, 2.5D) geometries.	是否有高程
object.is_ccw	Returns True if coordinates are in counter-clockwise order (bounding a region with positive signed area). This method applies to LinearRingobjects only	坐标序列是否是逆时针
object.is_empty	Returns True if the feature’s interior and boundary(in point set terms) coincide with the empty set.	空集判断
object.is_ring	Returns True if the feature is closed. A closed feature’s boundary coincides with the empty set.	闭环判断
object.is_simple	Returns True if the feature does not cross itself.	自相交判断
object.is_valid	Returns True if a feature is “valid”	合法性判断

Binary Predicates		二元谓词
object.almost_equals(other[, decimal=6])	Returns True if the object is approximately equal to the other at all points to specified decimal place precision.	相似性判断
object.almost_equals(other[, decimal=6])		相似性判断
object.contains(other)	Returns True if the object’s interior contains the boundary and interior of the other object and their boundaries do not touch at all.	包含
object.crosses(other)	Returns True if the interior of the object intersects the interior of the other but does not contain it, and the dimension of the intersection is less than the dimension of the one or the other.	内部交叉
object.disjoint(other)	Returns True if the boundary and interior of the object do not intersect at all with those of the other.	分离
object.equals(other)	Returns True if the set-theoretic boundary, interior, and exterior of the object coincide with those of the other.	相等
object.intersects(other)	Returns True if the boundary and interior of the object intersect in any way with those of the other.	相交
object.touches(other)	Returns True if the objects have at least one point in common and their interiors do not intersect with any part of the other.	接触
object.within(other)	Returns True if the object’s boundary and interiorintersect only with the interior of the other (not its boundary or exterior).	在内部

DE-9IM Relationships		九维关系谓词模型
object.relate(other)	Returns a string representation of the DE-9IM matrix of relationships between an object’s interior, boundary, exterior and those of another geometric object.	关系

Set-theoretic Methods		集论方法
object.boundary	Returns a lower dimensional object representing the object’s set-theoretic boundary.	边界
object.centroid	Returns a representation of the object’s geometric centroid (point).	图心
object.difference(other)	Returns a representation of the points making up this geometric object that do not make up the other object.	空间取反
object.intersection(other)	Returns a representation of the intersection of this object with the other geometric object.	取交集
object.symmetric_difference(other)	Returns a representation of the points in this object not in the other geometric object, and the points in the other not in this geometric object.	并集-交集
object.union(other)	Returns a representation of the union of points from this object and the other geometric object.	联合

Constructive Methods		建设方法
object.buffer	Returns an approximate representation of all points within a given distance of the this geometric object.	缓冲区
(distance, resolution=16,
cap_style=1, join_style=1,
mitre_limit=1.0)
object.convex_hull	Returns a representation of the smallest convex Polygon containing all the points in the object unless the number of points in the object is less than three.	凸包
object.envelope	Returns a representation of the point or smallest rectangular polygon (with sides parallel to the coordinate axes) that contains the object.	最小外包矩形
object.parallel_offset	Returns a LineString or MultiLineString geometry at a distance from the object on its right or its left side.	平移
(distance, side, resolution=16,
join_style=1, mitre_limit=1.0)
object.simplify(tolerance,	Returns a simplified representation of the geometric object.	简化
preserve_topology=True)		简化

Affine Transformations		仿射变化
shapely.affinity.affine_transform	Returns a transformed geometry using an affine transformation matrix.
(geom, matrix)
shapely.affinity.rotate	Returns a rotated geometry on a 2D plane.
(geom, angle, origin='center',
use_radians=False)
shapely.affinity.scale	Returns a scaled geometry, scaled by factors along each dimension.
(geom, xfact=1.0, yfact=1.0,
zfact=1.0, origin='center')
shapely.affinity.skew	Returns a skewed geometry, sheared by angles along x and y dimensions.
(geom, xs=0.0, ys=0.0,
origin='center', use_radians=False)
shapely.affinity.translate	Returns a translated geometry shifted by offsets along each dimension.
(geom, xoff=0.0, yoff=0.0, zoff=0.0)
shapely.ops.transform(func, geom)	Applies func to all coordinates of geom and returns a new geometry of the same type from the transformed coordinates.

Merging Linear Features		线性合并
shapely.ops.polygonize(lines)	Returns an iterator over polygons constructed from the input lines.	构面
shapely.ops.polygonize_full(lines)	Creates polygons from a source of lines, returning the polygons and leftover geometries.
shapely.ops.linemerge(lines)	Returns a LineString or MultiLineStringrepresenting the merger of all contiguous elements of lines.

Cascading Unions		级联合并
shapely.ops.cascaded_union(geoms)	Returns a representation of the union of the given geometric objects.
shapely.ops.unary_union(geoms)	Returns a representation of the union of the given geometric objects.

Prepared Geometry Operations		几何预操作
prepared.prep(ob)	Creates and returns a prepared geometric object.

Diagnostics		诊断
validation.explain_validity(ob)	Returns a string explaining the validity or invalidity of the object.

Interoperation--Well-Known Formats		wkt框架互操作
object.wkb.encode('hex')	A Well Known Text (WKT) or Well Known Binary(WKB) representation of any geometric object can be had via its wkt or wkb attribute.	wkb转wkt
object.wkt
shapely.wkb.dumps(ob)	Returns a WKB representation of ob.
shapely.wkb.loads(wkb)	Returns a geometric object from a WKB representation wkb.
shapely.wkt.dumps(ob)	Returns a WKT representation of ob.
shapely.wkt.loads(wkt)	Returns a geometric object from a WKT representation wkt.

Interoperation-- Numpy and Python Arrays		numpy和arrays互操作
shapely.geometry.asShape()	family of functions can be used to wrap Numpy coordinate arrays so that they can then be analyzed using Shapely while maintaining their original storage


Interoperation-- Python Geo Interface		geo接口互操作
shapely.geometry.asShape(context)	Adapts the context to a geometry interface. The coordinates remain stored in the context.
shapely.geometry.shape(context)	Returns a new, independent geometry with coordinates copied from the context.
shapely.geometry.mapping(ob)	Returns a new, independent geometry with coordinates copied from the context.

本文链接：https://blog.csdn.net/sinat_41310868/article/details/106699553

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