shp的基本操作

　　本节将介绍如何利用python完成对shp的基本操作

1.读取shp四至

import shapefile
sf = shapefile.Reader(r"E:\shp\1.shp")
#读取shp四至
min_x, min_y, max_x, max_y = sf.bbox

#读取每个图斑四至
shapes = sf.shapes()
arr = []
for i in range(0, len(shapes)):
    arr.append(shapes[i].bbox)

利用GDAL ogr读取shp图版四至，并添加到属性表中。

import os
from osgeo import ogr
# shp中添加四至
def shapes_boundary(shp_path):
    driver = ogr.GetDriverByName("ESRI Shapefile")
    dataSource = driver.Open(shp_path, 1)
    layer = dataSource.GetLayer()
    new_field1 = ogr.FieldDefn("minX", ogr.OFTReal)
    layer.CreateField(new_field1)
    new_field2= ogr.FieldDefn("minY", ogr.OFTReal)
    layer.CreateField(new_field2)
    new_field2 = ogr.FieldDefn("maxX", ogr.OFTReal)
    layer.CreateField(new_field2)
    new_field2 = ogr.FieldDefn("maxY", ogr.OFTReal)
    layer.CreateField(new_field2)
    t = int(layer.GetFeatureCount())
    for i in range(0, t):
        feat = layer.GetFeature(i)
        geom = feat.GetGeometryRef()
        minX = geom.GetEnvelope()[0]
        minY = geom.GetEnvelope()[2]
        maxX = geom.GetEnvelope()[1]
        maxY = geom.GetEnvelope()[3]
        feat.SetField("minX", minX)
        feat.SetField("minY", minY)
        feat.SetField("maxX", maxX)
        feat.SetField("maxY", maxY)
        layer.SetFeature(feat)
if __name__ == '__main__':
    shp=r"H:\test\1.shp"
    shapes_boundary(shp)

python利用ogr写入shp文件，定义shp文件属性字段（field）的数据格式为：

OFTInteger　　　　　　　# 整型
OFTIntegerList 　　　　# 整型list
OFTReal 　　　　　　　　# 双精度
OFTRealList 　　　　　 # 双精度list
OFTString 　　　　　　 # 字符
OFTStringList 　　　　 # 字符list
OFTWideString 　　　　 # 长字符
OFTWideStringList 　　# 长字符list
OFTBinary 　　　　　　　
OFTDate
OFTTime
OFTDateTime
OFTInteger64
OFTInteger64List
OFSTNone
OFSTBoolean
OFSTInt16
OFSTFloat32
OJUndefined

2.判断某个点是否在shp中

import shapefile
import shapely.geometry as geometry
import numpy as np
lons, lats = [], []
# lons = np.linspace(123.67, 123.32, 50)
# lats = np.linspace(23.48, 25.73, 25)
grid_lon, grid_lat = np.meshgrid(lons, lats)
flat_lon = grid_lon.flatten()
flat_lat = grid_lat.flatten()
flat_points = np.column_stack((flat_lon, flat_lat))
in_shape_points = []
sf = shapefile.Reader("E:/test/1.shp", encoding='gbk')
shapes = sf.shapes()
for pt in flat_points:
    if geometry.Point(pt).within(geometry.shape(shapes[0])):
        in_shape_points.append(pt)
        print("The point is in shp")
    else:
        print("The point is not in shp")
print(in_shape_points)

3.gdal生成shp

import osgeo.ogr as ogr
import osgeo.osr as osr

def run():
    driver = ogr.GetDriverByName("ESRI Shapefile")
    data_source = driver.CreateDataSource("Gooise.shp")
    srs = osr.SpatialReference()
    srs.ImportFromEPSG(32631)
    layer = data_source.CreateLayer("Gooise", srs, ogr.wkbPolygon)
    feature = ogr.Feature(layer.GetLayerDefn())
    #创建wkt文本
    wkt = 'polygon((646080 5797460,648640 5797460,648640 5794900,646080 5794900,646080 5797460))'
    polygon = ogr.CreateGeometryFromWkt(wkt)
    feature.SetGeometry(polygon)
    layer.CreateFeature(feature)
    feature = None
    data_source = None

4.shp拆分成多个shp

import osgeo.ogr as ogr
import osgeo.osr as osr

def create_shp(shp_name,wkt):
    driver = ogr.GetDriverByName("ESRI Shapefile")
    data_source = driver.CreateDataSource(f'E:/cq/tif/shp/{shp_name}.shp')
    srs = osr.SpatialReference()
    srs.ImportFromEPSG(4326)
    layer = data_source.CreateLayer(f'{shp_name}', srs, ogr.wkbMultiPolygon)
    feature = ogr.Feature(layer.GetLayerDefn())
    polygon = ogr.CreateGeometryFromWkt(wkt)
    feature.SetGeometry(polygon)
    layer.CreateFeature(feature)
    feature = None
    data_source = None

def run():
    driver = ogr.GetDriverByName('ESRI Shapefile')
    fileName = "E:/cq/中小河流.shp"
    dataSource = driver.Open(fileName, 0)
    layer = dataSource.GetLayer(0)
    print("空间参考 :{0}".format(layer.GetSpatialRef()))
    for i in range(0, layer.GetFeatureCount()):
        feat = layer.GetFeature(i)
        wkt = feat.geometry()
        print(wkt)
        create_shp(i, str(wkt))

if __name__ == '__main__':
    run()

5.基于gdal的面矢量面积计算

import ogr

def area(shpPath):
    '''计算面积'''
    driver = ogr.GetDriverByName("ESRI Shapefile")
    dataSource = driver.Open(shpPath, 1)
    layer = dataSource.GetLayer()
    new_field = ogr.FieldDefn("Area", ogr.OFTReal)
    new_field.SetWidth(32)
    new_field.SetPrecision(16)  # 设置面积精度,小数点后16位
    layer.CreateField(new_field)
    for feature in layer:
        geom = feature.GetGeometryRef()
        area = geom.GetArea()  # 计算面积
        # m_area = (area/(0.0089**2))*1e+6  # 单位由十进制度转为米
        # print(m_area)
        feature.SetField("Area", area)  # 将面积添加到属性表中
        layer.SetFeature(feature)
    dataSource = None

6.使用面积和Value值过滤矢量图层

import sys
from osgeo import ogr, osr, gdal

# 过滤矢量图层
def guolv(shp,mask,out,name):
    '''
    :param shp:shp路径
    :param mask:栅格路径，主要用来取投影信息
    :param out:输出路径
    :param name:文件名
    :return:None
    '''
    driver = ogr.GetDriverByName('ESRI Shapefile')
    dataSource = driver.Open(shp, 0)  # 0是只读，1可写
    if dataSource is None:
        print('could not open')
        sys.exit(1)
    # 获取图层
    layer = dataSource.GetLayer(0)
    t = int(layer.GetFeatureCount())
    drv = ogr.GetDriverByName('ESRI Shapefile')
    Polygon = drv.CreateDataSource(out)
    data = gdal.Open(mask, gdal.GA_ReadOnly)
    prj = osr.SpatialReference()
    prj.ImportFromWkt(data.GetProjection())
    # oLayer = Polygon.CreateLayer(name, srs=prj, geom_type=ogr.wkbMultiPolygon)
    oLayer = Polygon.CreateLayer(name, srs=prj, geom_type=ogr.wkbPolygon)
    oDefn = oLayer.GetLayerDefn()  # 定义要素
    gardens = ogr.Geometry(ogr.wkbPolygon)
    oFieldID = ogr.FieldDefn("ID", ogr.OFTInteger)  # 创建一个叫ID的整型属性
    oLayer.CreateField(oFieldID, 1)
    new_field1 = ogr.FieldDefn("minX", ogr.OFTReal)
    oLayer.CreateField(new_field1)
    new_field2= ogr.FieldDefn("minY", ogr.OFTReal)
    oLayer.CreateField(new_field2)
    new_field3 = ogr.FieldDefn("maxX", ogr.OFTReal)
    oLayer.CreateField(new_field3)
    new_field4 = ogr.FieldDefn("maxY", ogr.OFTReal)
    oLayer.CreateField(new_field4)
    feature = ogr.Feature(oLayer.GetLayerDefn())
    ID=0
    for i in range(0, t):
        feat = layer.GetFeature(i)
        wkt = (feat.geometry())
        geom = feat.GetGeometryRef()
        area = geom.GetArea()
        m_area = (area / (0.0089 ** 2)) * 1e+6
        v = feat.GetField('Value')
        # 面积过滤
        if m_area > 10000 and v==1:
            ID = ID+1
            polygon = ogr.CreateGeometryFromWkt(str(wkt))  ## 生成面
            minX = geom.GetEnvelope()[0]
            minY = geom.GetEnvelope()[2]
            maxX = geom.GetEnvelope()[1]
            maxY = geom.GetEnvelope()[3]

            feature.SetField("minX", float(minX))
            feature.SetField("minY", float(minY))
            feature.SetField("maxX", float(maxX))
            feature.SetField("maxY", float(maxY))

            feature.SetGeometry(polygon)  ## 设置面
            feature.SetField(0, ID)
            oLayer.CreateFeature(feature)