使用PyQGIS / Python与另一个图层的要素相交时是否拆分要素？

我有一个缓冲层（绿色多边形），当它越过障碍（蓝线）时，我想将其分成两个多边形。我一直在尝试使用“ splitGeometry”方法，但是我无法使其正常工作。到目前为止，我的代码是这样的：

while ldbuffprovider.nextFeature(feat):
  while barprovider.nextFeature(feat2):
    if feat.geometry().intersects(feat2.geometry()):
        intersection = feat.geometry().intersection(feat2.geometry())
        result, newGeometries, topoTestPoints=feat.geometry().splitGeometry(intersection.asPolyline(),True) 

结果（错误）返回1，newGeometries返回空列表。任何帮助是极大的赞赏。

为此，您可以使用对象的reshapeGeometry功能，该功能QgsGeometry沿与线的交点切割多边形。

以下将使缓冲区多边形与直线相交，并将分割的多边形要素添加到存储层（QGIS 2.0语法）：

# Get the dataProvider objects for the layers called 'line' and 'buffer'
linepr = QgsMapLayerRegistry.instance().mapLayersByName('line')[0].dataProvider()
bufferpr = QgsMapLayerRegistry.instance().mapLayersByName('buffer')[0].dataProvider()

# Create a memory layer to store the result
resultl = QgsVectorLayer("Polygon", "result", "memory")
resultpr = resultl.dataProvider()
QgsMapLayerRegistry.instance().addMapLayer(resultl)


for feature in bufferpr.getFeatures():
  # Save the original geometry
  geometry = QgsGeometry.fromPolygon(feature.geometry().asPolygon())
  for line in linepr.getFeatures():
    # Intersect the polygon with the line. If they intersect, the feature will contain one half of the split
    t = feature.geometry().reshapeGeometry(line.geometry().asPolyline())
    if (t==0):
      # Create a new feature to hold the other half of the split
      diff = QgsFeature()
      # Calculate the difference between the original geometry and the first half of the split
      diff.setGeometry( geometry.difference(feature.geometry()))
      # Add the two halves of the split to the memory layer
      resultpr.addFeatures([feature])
      resultpr.addFeatures([diff])

使用SQLite和SpatiaLite编译的GDAL> = 1.10.0可以很好地近似于将图层（例如poligon.shp和line.shp）包装在OGR VRT文件（例如，layers.vrt）中：

<OGRVRTDataSource>
    <OGRVRTlayer name="buffer_line">
        <SrcDataSource>line.shp</SrcDataSource>
        <SrcSQL dialect="sqlite">SELECT ST_Buffer(geometry,0.000001) from line</SrcSQL>
    </OGRVRTlayer>
    <OGRVRTlayer name="polygon">
        <SrcDataSource>polygon.shp</SrcDataSource>
    </OGRVRTlayer>
</OGRVRTDataSource>

为了在line.shp周围有一个非常小的缓冲区（例如1微米），请获得* buffer_line *层。然后，我们可以使用SpatiaLite在这些几何上应用对称差和差：

ogr2ogr splitted_polygons.shp layers.vrt -dialect sqlite -sql "SELECT ST_Difference(ST_SymDifference(g1.geometry,g2.geometry),g2.geometry) FROM polygon AS g1, buffer_line AS g2" -explodecollections

显然，所有这些东西都可以从Python脚本完美执行：

os.system("some_command with args")

希望这可以帮助！

杰克（Jake）的答案与分裂的多边形有关的拓扑问题。我提出了一个解决方案，希望对您有所帮助：https : //gist.github.com/RamonLopezEscudero/844c1401f5339143da1b2b5cf7ff27bd