Welcome to centerline’s documentation!

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Roads, rivers and similar linear structures are often represented by long and complex polygons. Since one of the most important attributes of a linear structure is its length, extracting that attribute from a polygon can prove to be more or less difficult.

This library tries to solve this problem by creating the the polygon’s centerline using the Voronoi diagram.


The source and the output geometry visualized in QGIS.


  • A command-line script for creating centerlines from a vector source file and saving them into a destination vector file: create_centerlines

$ create_centerlines input.shp output.geojson
  • The Centerline class that allows integration into your own workflow.

>>> from shapely.geometry import Polygon
>>> from centerline.geometry import Centerline

>>> polygon = Polygon([[0, 0], [0, 4], [4, 4], [4, 0]])
>>> attributes = {"id": 1, "name": "polygon", "valid": True}

>>> centerline = Centerline(polygon, **attributes)
>>> centerline.id == 1
>>> centerline.name
>>> centerline.geoms
<shapely.geometry.base.GeometrySequence object at 0x7f7d24116210>

Indices and tables