Image processing using opencv often involves reading data from a file into cv::Mat or writing data from cv::Mat to an txt file.

Here is a common method I use to write data from cv::Mat to an txt file, as shown in the code:

void writeMatToFile(cv::Mat& m, const char* filename)
{
 std::ofstream fout(filename);

 if (!fout)
 {
 std::cout << "File Not Opened" << std::endl;
 return;
 }

 for (int i = 0; i<m.rows; i++)
 {
 for (int j = 0; j<m.cols; j++)
 {
 fout << m.at<float>(i, j) << "\t";
 }
 fout << std::endl;
 }

 fout.close();
}