What algorithms are out there for detecting lights and shadows and their parameters?

Question

So I have picture (not the best one)

I want to detect where the lights come from and what types of lights are they. What algorithm\framework can do such things with static images?

I mentioned shadows because in general if you can separate a shadow from a surface than you can probably determine light type and other its parameters.

I mean general shadows search not only for presented image.

Answer 1

With the image that you presented, there are so many sources of error that I'd be surprised if a trained human, let alone an algorithm could do better than ±20% on any calculations. Here are the problems:

1. There isn't a known straight line anywhere since everything is hand hewn. The best bet would be the I-beam above the doorway but you don't know it's orientation.
2. There's heavy barrel distortion in the edges of the image which are introduced by the lens and are characteristic of that lens at that zoom and focus. Without precise calibration of that, you can only guess at the degree of distortion.
3. The image is skewed with regard to the wall it is facing but none of the walls appear to be all that planar anyway.
4. You want to know the source of lights. Well the obvious primary light is the sun, but latitude, longitude, time and date all affect that. Then there are the diffuse reflections but unless you have the albedo of the materials you can only guess.

What are you hoping to derive from this image? Usually when doing lighting analysis, someone will put known reference targets of different, known reflectivity in the space to be analyzed. Working from a pocket snapshot camera on an unknown scene really limits what you can extrapolate.