def xform(extent, srcCRS, destCRS):
if srcCRS == destCRS:
return extent # nothing to do
# cut down the extent so it's not too big
# clamped to the projection's valid area (usually small)
projectionClampedExtent = clampToProjectionExtent(extent, srcCRS)
# clamped to the world (might not work in some projections)
worldClampedExtent = clampToWorld(extent, srcCRS)
# xform the two extents to the dest CRS
transform = QgsCoordinateTransform(srcCRS, destCRS, QgsProject.instance())
xformed_projectionClamped = QgsRectangle() # null rect
if not projectionClampedExtent.isNull():
xformed_projectionClamped = transform.transformBoundingBox(projectionClampedExtent)
xformed_worldClamped = QgsRectangle() # null rect
if not worldClampedExtent.isNull():
xformed_worldClamped = transform.transformBoundingBox(worldClampedExtent)
# make final choice of what to use
# we WANT to use the world one, but sometimes cannot
# indicates everything is ok -- likely no projection blowing up
if xformed_worldClamped.contains(xformed_projectionClamped):
return xformed_worldClamped # likely good
# if one is null, return the other
if xformed_projectionClamped.isNull():
return xformed_worldClamped
if xformed_worldClamped.isNull():
return xformed_projectionClamped
# clamp to the destination CRS (last resort to try to get something valid)
return clampToProjectionExtent(xformed_worldClamped, destCRS)
