Applying reverse QgsCoordinateTransform on QgsGeometry in PyQGIS

Question

I have defined xform as a QgsCoordinateTransform to project geographic coordinates.

I can use:

unprojPoint = xform.transform(point, QgsCoordinateTransform.ReverseTransform)

to do the reverse operation, but how can I apply this to a QgsGeometry?

I can do:

line.transform(xform)

alright, but this won't take a direction argument.
I would expect something along the lines of:

line.transform(xform, QgsCoordinateTransform.ReverseTransform)

would work but no luck...

Do I have to set up a new QgsCoordinateTransform to do this?

Note: I am using QGIS 3.0

Answer 1

You can do this if you dig into the low-level QgsAbstractGeometry API. Try:

line_data = line.constGet().clone()

try:
    line_data.transform(xform, QgsCoordinateTransform.ReverseTransform)
except:
    # catch transform errors!
    pass

transformed_line = QgsGeometry(line_data)