Function camera_calibration_parser::readCalibrationIni() fails if the INI file is read-only

[dfischer42]

Our calibration data is usually read-only to prevent accidental modifications. Unfortunately, this becomes a problem when the data is stored as an INI file, as the function camera_calibration_parser::readCalibrationIni() uses

std::fstream fs(file_name);

By default, files are opened in read-write mode in this way. With read-only files, this inevitably leads to an error. Simple solution is to use std::istream instead of std::fstream. For the time being, our local version uses

bool readCalibrationIni(
  const std::string & file_name, std::string & camera_name,
  CameraInfo & cam_info)
{
  std::ifstream fs(file_name);
  return readCalibrationIni(fs, camera_name, cam_info);
}

and works as expected. It would be nice to see this fixed.