Create a box the bounds them into smallest possible box.

Hi guys.. I am trying to bound some points into a box (Rect).. The problem is though the box becomes to large, even though I use boundingRect.. I am trying to box the features The sample code Surf detect on a image. Code can be seen here. http://docs.opencv.org/doc/tutorials/features2d/feature_homography/feature_homography.html I want to retract the green square to a rect.