Canvas rotate from bottom center image angle?

Question

How do you rotate an image with the canvas html5 element from the bottom center angle?

Answer 1

The correct answer is, of course, Vincent's one.
I fumbled a bit with this rotation/translation thing, and I think my little experiments could be interesting to show:

My stumbling issue was that positioning the rotated figure is hard, because it is along the rotated axis: either we have to do some trigo math to paint at the primitive origin, or we have to draw on a secondary hidden canvas and then paint it on the target one.
Unless somebody else has a better idea?