How can I measure the level of ambient light from an image?

Question

I am looking at making an app that uses a camera to measure the amount of light present when an image is taken. Some conditional behavior would take place based on how much

Answer 1

First random thought, something like a threshold filter to remove "objects" take whats left from the source image and threshold it again, count white vs black pixels, should give you a VERY rough idea of light vs dark. Thresholding