Anna Kettle coughed up some electrons that declared:

I have a photo which was taken looking upwards to high on a wall and I
want to deform it to get a picture looking straight on. Now it seems
to me that there ought to be some software gizmo to do this but what
is it called? Googling on picture deformation doesnt come up with
anything useful

Anna

Here you go Anna,

http://www.dionic.net/wibble.png

That shows Gimp with a photo loaded and the correct tool (the depressed
button on the top left window). Set the same settings in the middle left
window ("corrective" mode is the crucial one), set teh grid (just click and
drag corners about) in the main picture.

The aim is to line the grid lines up with things you believe should be
parallel, eg the vertices of your building.

Hit "Transform" on the bottom left window - job done. Save file. CTRL-Z
or "Undo" goes back if you don;t like it.

http://gimp-win.sourceforge.net/stable.html

Gets you Gimp for Windows - just run the installer. Better than anything
else that's free, true open source, competently built for Windows as well
and Linux and Mac. It's a bit like photoshop but with less plugins and
rather less money!

Cheers

Tim