How can I exclude certain keypoint from matching?

edit

Hi,

I have two cv::Mat with descriptors desc1 and desc2.

Now I want to perform a matching of these key points in two steps.

First step: Match all descriptors in desc1 with desc2 (excluding 1, 5, 8, 9 for example) Second step: Match descriptors in desc1 that where not matched in first step with following descriptors in desc2 (1, 5, 8, 9).

I hope that you understand what I mean. I think this should be possible using masks. But how?

Thanks in advance!