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I vectorised an image and all my polygons have extremely jagged edges. What is the best way to smooth these polygons?

enter image description here

marked as duplicate by PolyGeo May 22 at 9:16

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  • 1
    Do you want to display them smoothly, or do you actually want to smooth them? – Erik May 22 at 8:28
  • I would try slight simplification followed by smoothing, but with that much jaggering the result may not be so great. If you could offer test data people might get interested in doing some experiments. – user30184 May 22 at 8:30
  • Erik, i want to smooth the polygons. – user143448 May 22 at 8:46
  • we.tl/t-ee3Nmb3UOh Here is a link to a sub dataset – user143448 May 22 at 9:05
  • It looks like many of the polygon edges follow straight lines, so you could manually draw some lines and use the snap geometries to layer tool. – csk May 22 at 20:34

Two possible options here: Simplify vs Smoothing (both accessible from Locator bar or the Processing toolbox)

With Simplify, the algorithm simplifies the geometries creating a new layer with geometries containing a lower number of vertices. That leads to reduce the jagged shapes.

Alternatively, you can make use of Smooth. This algorithm smooths the geometries while creates a new layer with geometries containing a higher number of vertices and corners in the geometries smoothed out. This will turn your jagged shapes in a more soften geometries. You can try several values for iteration and node angles to see what happens.

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