Need to ignore black rectangluar blobs which are not on the mat

We are working on a robotics competition and have to solve a mat using a robot. The mat will be kept on the floor and it will have a black border around it.
How can i ignore all the black blobs which the camera detects that are not on the mat? Is there any specific parameter to be set in fand_blobs to do that? Kindly respond.

Yeah, you just detect the mat blob using find_blobs() and then look at all rects of detected blobs that are inside the mat blob. This is a very simple intersection of rects problem.