Centreline for vectors

Question

I'm trying to get a centreline representation for some polygon output from OSM but having tried the approach in this post (Skeletonize vectors in QGIS/Python) I'm getting very odd results. Here's the polygon, the output from and the 'centreline' given by v.voronoi.skeleton with the smoothness set to 0.01.

You can see this has resulted in a lot of points. If I don't set the smoothness that low I end up with lots of jagged sections that aren't oriented in the direction of the line.

What is the recommended approach to get to a final output that is like the following with right angles and points merged into longer line sections?

I'm trying to do this programmatically for x number of polygons.

EDIT: I've found using 'Simplify' and tweaking some of the settings can give close to the desired result, although orientation of the final line can be off.

Answer 1

As you are looking for a programatical solution... you could check out pygeoops.centerline. It also uses voronoi polygons as a basis to create the centerline, but also removes short branches, simplifies the result,... to get a "clean" result.

Sample script:

import pygeoops
import shapely

polygon = shapely.from_wkt("POLYGON ((0 0, 0 8, -2 10, 4 10, 2 8, 2 2, 10 2, 10 0, 0 0))")
centerline = pygeoops.centerline(polygon)

Result:

Disclaimer: I'm the developer of pygeoops