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Change MultiLineString direction in QGIS/PyQGIS

How can I switch line direction in QGIS?

0

I am looking for a method in PyQGIS (QGIS3.x) of reversing the direction of a MultiLineString feature.

I have found a similar question -
How can I switch line direction in QGIS? - for LineString/Polyline. - which only works for QGIS2 - and modified it slightly for use in QGIS3. However, I can't work out how to adapt the approach for MultiLineStrings.

layer = qgis.utils.iface.mapCanvas().currentLayer()

fid = 1 # feature id

feature = layer.getFeature(1)

geom = feature.geometry()

nodes = geom.asPolyline()

nodes.reverse() 

newgeom = QgsGeometry.fromPolylineXY(nodes)

layer.startEditing()

layer.changeGeometry(feature.id(),newgeom)

layer.commitChanges()

In theory the above approach could be used with
newgeom = QgsGeometry.fromMultiPolylineXY()
but I can't see how to generate the necessary QgsMultiPolylineXY object.

I have also noted the reversed() function on the QGSMultiLineCurve class, but I couldn't attach the generated QGSMultiLineCurve to the original feature.

I'm not really interested in UI-based approaches, as the features to be reversed are determined programatically.

Any approaches are welcome - if there's a better general approach than above, I'm happy to hear.

qgis pyqgis direction

share

asked 16 secs ago

Tom BrennanTom Brennan

11

add a comment | 

0

I am looking for a method in PyQGIS (QGIS3.x) of reversing the direction of a MultiLineString feature.

I have found a similar question -
How can I switch line direction in QGIS? - for LineString/Polyline. - which only works for QGIS2 - and modified it slightly for use in QGIS3. However, I can't work out how to adapt the approach for MultiLineStrings.

layer = qgis.utils.iface.mapCanvas().currentLayer()

fid = 1 # feature id

feature = layer.getFeature(1)

geom = feature.geometry()

nodes = geom.asPolyline()

nodes.reverse() 

newgeom = QgsGeometry.fromPolylineXY(nodes)

layer.startEditing()

layer.changeGeometry(feature.id(),newgeom)

layer.commitChanges()

In theory the above approach could be used with
newgeom = QgsGeometry.fromMultiPolylineXY()
but I can't see how to generate the necessary QgsMultiPolylineXY object.

I have also noted the reversed() function on the QGSMultiLineCurve class, but I couldn't attach the generated QGSMultiLineCurve to the original feature.

I'm not really interested in UI-based approaches, as the features to be reversed are determined programatically.

Any approaches are welcome - if there's a better general approach than above, I'm happy to hear.

qgis pyqgis direction

share

asked 16 secs ago

Tom BrennanTom Brennan

11

add a comment | 

I am looking for a method in PyQGIS (QGIS3.x) of reversing the direction of a MultiLineString feature.

I have found a similar question -
How can I switch line direction in QGIS? - for LineString/Polyline. - which only works for QGIS2 - and modified it slightly for use in QGIS3. However, I can't work out how to adapt the approach for MultiLineStrings.

layer = qgis.utils.iface.mapCanvas().currentLayer()

fid = 1 # feature id

feature = layer.getFeature(1)

geom = feature.geometry()

nodes = geom.asPolyline()

nodes.reverse() 

newgeom = QgsGeometry.fromPolylineXY(nodes)

layer.startEditing()

layer.changeGeometry(feature.id(),newgeom)

layer.commitChanges()

In theory the above approach could be used with
newgeom = QgsGeometry.fromMultiPolylineXY()
but I can't see how to generate the necessary QgsMultiPolylineXY object.

I have also noted the reversed() function on the QGSMultiLineCurve class, but I couldn't attach the generated QGSMultiLineCurve to the original feature.

I'm not really interested in UI-based approaches, as the features to be reversed are determined programatically.

Any approaches are welcome - if there's a better general approach than above, I'm happy to hear.

qgis pyqgis direction

share

asked 16 secs ago

Tom BrennanTom Brennan

11

layer = qgis.utils.iface.mapCanvas().currentLayer()

fid = 1 # feature id

feature = layer.getFeature(1)

geom = feature.geometry()

nodes = geom.asPolyline()

nodes.reverse() 

newgeom = QgsGeometry.fromPolylineXY(nodes)

layer.startEditing()

layer.changeGeometry(feature.id(),newgeom)

layer.commitChanges()

share

asked 16 secs ago

Tom BrennanTom Brennan

11

share

asked 16 secs ago

Tom BrennanTom Brennan

11

asked 16 secs ago

Tom BrennanTom Brennan

11

asked 16 secs ago

Tom BrennanTom Brennan

11