[OpenCV]operation

gistfile1.cpp

// create random Mat
int rows = 10, cols = 10;
cv::Mat m = cv::Mat::zeros(rows, cols, CV_32F);
cv::RNG(cv::getTickCount().fill(m, cv::RNG::UNIFORM, cv::Scalar(0), cv::Scalar(1));

// or you can use randu and randn. I prefer RNG, because I can set the seed.
randu(m, cv::Scalar(0), cv::Scalr(1));

// change one line
cv::mat row = m.row(0);
row = cv::Mat::ones(1, m.cols, m.type());

// if want to replace one line with a line in t
cv::Mat t = cv::Mat::zeros(rows, cols, CV_32F);
cv::RNG(cv::getTickCount().fill(t, cv::RNG::UNIFORM, cv::Scalar(0), cv::Scalar(1));

t.row(2).copyTo(row);

// cv::Mat normalize to 1
void normalize_mat(cv::Mat &m)
{
    assert(m.rows == 1);
    float sum = cv::sum(m)[0];
    // cv::multiply(m, cv::Mat::ones(cv::Size(m.cols, m.rows), CV_32F), m, 1./sum);
    m = m*(1./sum);
    for(int i=0; i<m.cols; ++i) {
        m.at<float>(0, i) += m.at<float>(0, i-1);
    }
    m.at<float>(0, m.cols) = 1;             // resolve precision problem
}