Thanks chazfenn for your suggestion. I think Gimp has a facility to do this.
Thanks Gary for your clarification and for confirming chazfenn's suggestion. By the way what does the abbreviation 'sw' mean?
I have a photo of my house taken by one of these companies in a plane.
It's a sideways but angled down shot and I would like to convert it fully to a bird's eye view, i.e. looking down on on the house.
Is there software or a trick that can do this?