I'm trying to remove the background from a photo with a subject, but I would prefer not need to use this kind of techniques to select the background. Some magic-fu would select the shape since it's easy enough to identify the subject from two identical pictures, one with and another without the subject.
(Just as an additional point, in the link above the background is very simple so it is easy to use the magic-wand; a more complex background would not be so easy to deal with. However, if the technique I'm looking for exists, I would expect the same level of difficulty for both backgrouns)
Which were, in the real case, obviously obtained through photographing and not digital editing.
I thought it would be possible to do this automatically if I had a picture of the background without the subject. Sort of, programmatically, remove every repeated pixel and only keep the different ones.
Although this makes sense to me I can't find instructions on how to do this. Maybe because I don't even know how to search.
Background to greenscreen doesn't seem to be it.
I'm using GIMP, but if you know how to do it using other application, I can try to "convert" the instructions.