CSV with OpenCV cv::Mat

#include <opencv2/core/core.hpp>
#include <opencv2/core/mat.hpp>
#include <opencv2/core/operations.hpp>
#include <algorithm>
#include <cstdint>
#include <fstream>
#include <iostream>
#include <string>

cv::Mat parseCSV(const std::string& path) {
  std::ifstream fin { path };
  std::uint32_t row_size = 0, col_size = 0;

  while (!fin.eof()) {
    std::string line;
    std::getline(fin, line);
    if (line.empty())
      break;
    row_size++;
    std::uint32_t col = std::count(line.begin(), line.end(), ',');
    col++;
    col_size = std::max(col, col_size);
  }
  fin.clear();
  fin.seekg(0);

  cv::Mat_<int> new_m(row_size, col_size);
  std::uint32_t i = 0, j = 0;
  while (!fin.eof()) {
    std::string line;
    std::getline(fin, line);
    if (line.empty())
      break;
    std::istringstream line_stream { line };
    for (std::string s; std::getline(line_stream, s, ',');) {
      new_m(i, j++) = std::stoi(s);
    }
    ++i;
    j = 0;
  }
  fin.close();
  return new_m;
}

void writeCSV(const std::string& path, const cv::Mat& m) {
  std::ofstream fout { path };
  fout << cv::format(m, "csv");
  fout.close();
}

int main() {
  std::string path { "data.csv" };
  cv::Mat m = parseCSV(path);
  m.at<int>(0, 0) = 100;
//  std::cout << m << std::endl;
  path = "new_" + path;
  writeCSV(path, m);
}