How to calculate the background intensity of grayscale image?

How do i calculate the background intensity at each pixel of an grayscale image

Answer 1

[Image Analyst]

It depends. If you can, just snap an image without your foreground in there. Like if it's a hand in front of a white sheet, snap a photo of just the white sheet alone, without the hand in there. If you can't do that and need to estimate the background from the actual image, then try to identify the foreground and use some algorithm to fill in those pixels with background, like use regionfill(), or fit the whole background mask to a 2-D polynomical, or use some morphological methods, etc. You forgot to attach your image(s) so I can't really offer better advice.

[Image Analyst]

Since you don't know for certain the background behind the person, the easiest way is to simply take a photo of the background without any person there. Only that way can you know what the background intensity of every pixel in the image is. Otherwise you'd be guessing. It should be easy to get that image without a person in the image, right?