Method batchDistance

deps/opencv/modules/core/src/stat.cpp:2473–2582

}

void cv::batchDistance( InputArray _src1, InputArray _src2,
                       OutputArray _dist, int dtype, OutputArray _nidx,
                       int normType, int K, InputArray _mask,
                       int update, bool crosscheck )
{
    Mat src1 = _src1.getMat(), src2 = _src2.getMat(), mask = _mask.getMat();
    int type = src1.type();
    CV_Assert( type == src2.type() && src1.cols == src2.cols &&
              (type == CV_32F || type == CV_8U));
    CV_Assert( _nidx.needed() == (K > 0) );

    if( dtype == -1 )
    {
        dtype = normType == NORM_HAMMING || normType == NORM_HAMMING2 ? CV_32S : CV_32F;
    }
    CV_Assert( (type == CV_8U && dtype == CV_32S) || dtype == CV_32F);

    K = std::min(K, src2.rows);

    _dist.create(src1.rows, (K > 0 ? K : src2.rows), dtype);
    Mat dist = _dist.getMat(), nidx;
    if( _nidx.needed() )
    {
        _nidx.create(dist.size(), CV_32S);
        nidx = _nidx.getMat();
    }

    if( update == 0 && K > 0 )
    {
        dist = Scalar::all(dtype == CV_32S ? (double)INT_MAX : (double)FLT_MAX);
        nidx = Scalar::all(-1);
    }

    if( crosscheck )
    {
        CV_Assert( K == 1 && update == 0 && mask.empty() );
        Mat tdist, tidx;
        batchDistance(src2, src1, tdist, dtype, tidx, normType, K, mask, 0, false);

        // if an idx-th element from src1 appeared to be the nearest to i-th element of src2,
        // we update the minimum mutual distance between idx-th element of src1 and the whole src2 set.
        // As a result, if nidx[idx] = i*, it means that idx-th element of src1 is the nearest
        // to i*-th element of src2 and i*-th element of src2 is the closest to idx-th element of src1.
        // If nidx[idx] = -1, it means that there is no such ideal couple for it in src2.
        // This O(N) procedure is called cross-check and it helps to eliminate some false matches.
        if( dtype == CV_32S )
        {
            for( int i = 0; i < tdist.rows; i++ )
            {
                int idx = tidx.at<int>(i);
                int d = tdist.at<int>(i), d0 = dist.at<int>(idx);
                if( d < d0 )
                {
                    dist.at<int>(idx) = d;
                    nidx.at<int>(idx) = i + update;
                }
            }
        }