Reliable method for detecting dark clothing against dark background

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Hello,

I'm trying to reliably determine where a person is in a room with a black, partially reflective floor. Sometimes they wear black pants and it prevents my blob detection from picking them up. I have tried taking a picture of an empty room and performing a difference with the current image to find out where they are, and I have also tried some basic motion detection to bring them out, but none have overcome the dark clothing issue.

I am wondering about a depth-map-based solution, but my equipment will be between 5 and 10 meters away from my subject, so I'm not sure if the readily available Kinect sensor would work well. Do any of you deal with a similar challenge? Any "best practices" as to how I can bring my subject out of the background?

Thanks!