Overlap / Combine two image

Is there any idea to combine/overlap two images into one? I would like to combine the foreground and background in this image.

http://i43.tinypic.com/2qxrjwo.jpg

I wish only the human image remained after the fusion, but after I tried it, the background did not turn to be totally black. Is there any idea to enhance it? Thank you.

Answer 1

[Anton Semechko]

By convention foreground is usually white (pixel value = 1) and background is black (pixel value = 0). Suppose IM is your original grayscale image and BW is a binary image of the same size as IM, where positive pixels (i.e. those that have value = 1) belong to the foreground. To subtract the background from IM, do the following:

IM(~BW)=0;

[Syahrul Niezam]

Thanks a lot! :)