poor-mans-spy.cpp

/*
 * Example: spy("foobar.ppm", A);
 */
int spy(std::string const& ppmfile, arma::mat const& M) {
  ofstream ofs(ppmfile);

  if (!ofs.is_open())
    return -1;

  ofs << "P3\n" << M.n_rows << " " << M.n_cols << "\n1\n";

  for (unsigned i = 0; i < M.n_rows; ++i) {
    for (unsigned j = 0; j < M.n_cols; ++j) {
      for (unsigned k = 0; k < 3; ++k)
        ofs << (M(i, j) == 0) << " ";

      ofs << "  ";
    }

    ofs << "\n";
  }

  return 0;
}