Can you limit the number of Keypoints using sift feature detector?

edit

You can limit the Keypoints if you use ORB detector.

You cannot set number of key pointsUse first parameter nfeature of create method

    Mat img=imread("f:/lib/opencv/samples/data/lena.jpg",IMREAD_COLOR);
    for (int i=0;i<5;i++)
    {
        Mat desc;
        vector<KeyPoint> p;
        Ptr<xfeatures2d::SIFT> b= xfeatures2d::SIFT::create(i*100);
        b->detectAndCompute(img,Mat(),p,desc);
        cout<< p.size()<<"\t"<<desc.rows<<"\n";
    }
}

Results :

1111    1111 
100     100 
200     200
300     300 
400     400

but you can try too as suggested in doc to reduce keypoint number:

1. increase contrastThreshold
2. increase sigma
3. decrease edge threshold