Thanks. I haven't tried that specifically but assume it should work. If the image has 2 clear straight up and down objects/edges in it (with some distance between them), extend those lines up or down until they converge, that'll be the vertical vanishing point. If there aren't clear vertical indications in the image, then the cone of vision could be the answer. It can get tricky if the image was cropped (that would shift the center point) or if it was shot with a lens that creates distortion (wide lenses or cheap ones).
