Rectangle identification

[cooltext]

Does any one know how to make an algorithm that is able to identify solely the the rectangle we are tracking even at angles? See, our problem is that when we only use the threshold we still have other targets such as the lights and windows. And when we use the algorithms in the whitepaper, it only works when we are in front of the robot. So could someone post there code for identifying rectangles or explain what the did?
thanks