how to publish sensor_msgs::CameraInfo messages ?

edit

The recommended method is to use image_transport and camera_info_manager.

Here's how camera1394 does it:

  /** Publish camera stream topics
   *
   *  @param image points to latest camera frame
   */
  void Camera1394Driver::publish(const sensor_msgs::ImagePtr &image)
  {
    image->header.frame_id = config_.frame_id;

    // get current CameraInfo data
    sensor_msgs::CameraInfoPtr
      ci(new sensor_msgs::CameraInfo(cinfo_->getCameraInfo()));

    // check whether CameraInfo matches current video mode
    if (!dev_->checkCameraInfo(*image, *ci))
      {
        // image size does not match: publish a matching uncalibrated
        // CameraInfo instead
        if (calibration_matches_)
          {
            // warn user once
            calibration_matches_ = false;
            ROS_WARN_STREAM("[" << camera_name_
                            << "] calibration does not match video mode "
                            << "(publishing uncalibrated data)");
          }
        ci.reset(new sensor_msgs::CameraInfo());
        ci->height = image->height;
        ci->width = image->width;
      }
    else if (!calibration_matches_)
      {
        // calibration OK now
        calibration_matches_ = true;
        ROS_WARN_STREAM("[" << camera_name_
                        << "] calibration matches video mode now");
      }

    // fill in operational parameters
    dev_->setOperationalParameters(*ci);

    ci->header.frame_id = config_.frame_id;
    ci->header.stamp = image->header.stamp;

    // @todo log a warning if (filtered) time since last published
    // image is not reasonably close to configured frame_rate

    // Publish via image_transport
    image_pub_.publish(image, ci);
  }