int diff_count(const Mat& lmat, const Mat& rmat, int threshold) {
    int cols = lmat.cols;
    int rows = lmat.rows;
    int esize = (int)lmat.elemSize();

    if ( rmat.cols != cols || rmat.rows != rows || (int)rmat.elemSize() != esize ) {
        return -1;
    }

    int total = rows * cols;
    int dcount = 0;

    for ( int i = 0; i < total; i++ ) {
        uchar* lptr = lmat.data + i*esize;
        uchar* rptr = rmat.data + i*esize;

        int sum = 0;
        for ( int j = 0; j < esize; j++ ) {
            uchar lu = lptr[j];
            uchar ru = rptr[j];

            int tmp = lu > ru ? lu - ru : ru - lu;
            sum += tmp*tmp;
        }

        if ( sqrt(sum)/esize >= threshold ) {
            dcount++;
        }
    }

    return dcount;
}