pygeoops.centerline

pygeoops.centerline(geometry, densify_distance: float = -1, min_branch_length: float = -1, simplifytolerance: float = -0.25, extend: bool = False) → BaseGeometry | ndarray[tuple[Any, ...], dtype[BaseGeometry]] | GeoSeries | None

Calculates an approximated centerline for a polygon.

Negative values for the algorithm parameters will result in an automatic optimisation based on the average geometry width for each input geometry.

Alternative name: medial axis.

Example output with default parameters (grey: original polygon, blue: centerline):

(Source code, png, hires.png, pdf)

Parameters:

• geometry (geometry, GeoSeries or arraylike) – a geometry, GeoSeries or arraylike.

• densify_distance (float, optional) –

  densify input geometry so each segment has maximum this length. A reasonable value is the typical minimal width of the input geometries. If a larger value is used centerlines might have holes on narrow places in the input geometry. The smaller the value choosen, the longer the processing will take. Defaults to -1.

  • value = 0: no densification

  • value > 0: densify using this value

  • value < 0: densify_distance = average width of geometry * abs(value)

• min_branch_length (float, optional) –

  minimum length for branches of the main centerline. Defaults to -1.

  • value = 0: no branch filtering

  • value > 0: filter branches shorter than this value

  • value < 0: min_branch_length = average width of geometry * abs(value)

• simplifytolerance (float, optional) –

  tolerance to simplify the resulting centerline (using Douglas-Peucker algoritm). Defaults to -0.25.

  • value = 0: no simplify

  • value > 0: simplify with this value as tolerance

  • value < 0: simplifytolerance = average width of geometry * abs(value)

• extend (bool, optional) – extend the centerline to the edge of the geometry.

Returns:

the centerline for each of the input

geometries.

Return type:

geometry, GeoSeries or array_like

Examples

These are some more visualisation of centerlines calculated with some different options specified.

(Source code, png, hires.png, pdf)