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Two geometries can be clipped in various ways. I have expected the same result, but I got two different results. The following method I used.

I have selected the clip function and added two layers. The green feature is the correct result. The geometry has been clipped by the blue layer. Then I get the following result:

enter image description here

All processing commands are available from the QGIS built-in Python console. I used the function 'qgis: clip'.

processing.runandload('qgis:clip', layer1, layer2, None)

Then I get the following incorrect result:

enter image description here

It seems to me as if the blue layer is empty or is ignored.

What am I doing wrong?

Update:

The Feature (orange frame, layer1) should be cut at the blue layer (layer2).

enter image description here

What I do not understand is why the clip function of QGIS works. To find under: Vector -> Geoprocessing Tools -> Clip.

enter image description here

When I run the following code, I get an incorrect result:

processing.runandload('qgis:clip', layer1, layer2, None)

Even if I reverse the two layers, I get the same result:

enter image description here

Why I do not get the same result? Take the tools not the same clip function?

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  • Where do layer1 and layer2 come from? Is there any output in the message log, processing tab? Or in the processing history?
    – Matthias Kuhn
    Commented Apr 4, 2016 at 14:27
  • Did you try switching layer1 and layer2 (e.g. processing.runandload('qgis:clip', layer2, layer1, None)?
    – Joseph
    Commented Apr 4, 2016 at 14:27
  • I've updated my question.
    – eftas
    Commented Apr 5, 2016 at 8:35
  • To me it simply looks like you switched layer 1 and 2 in the second approach. Would be helpful if you provide images of layer 1 and 2 alone. So it's easier to understand which layers you are using and want to clip.
    – Generic Wevers
    Commented Apr 5, 2016 at 9:18
  • Even if I reverse the two layers, I get the same incorrect result
    – eftas
    Commented Apr 8, 2016 at 14:12

1 Answer 1

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I now use the function intersection. Returns a geometry representing the points shared by this geometry and other. This function gives me the desired result.

See: QgsGeometry::intersection

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