wpr_simulation2/exercises/9_cv_save_file.cpp

#include <rclcpp/rclcpp.hpp>
#include <sensor_msgs/msg/image.hpp>
#include <cv_bridge/cv_bridge.h>
#include <opencv2/imgproc/imgproc.hpp>
#include <opencv2/highgui/highgui.hpp>

std::shared_ptr<rclcpp::Node> node;

void CamRGBCallback(const sensor_msgs::msg::Image::SharedPtr msg)
{
    cv_bridge::CvImagePtr cv_ptr;
    cv_ptr = cv_bridge::toCvCopy(msg, sensor_msgs::image_encodings::BGR8);

    cv::Mat imgOriginal = cv_ptr->image;
    cv::imshow("RGB", imgOriginal);
    cv::waitKey(1);

    // Save the image to file
    cv::imwrite("/home/robot/image.jpg",imgOriginal);
    printf("Saved the image to file!\n");
}

int main(int argc, char **argv)
{
    rclcpp::init(argc, argv);
    node = std::make_shared<rclcpp::Node>("cv_save_file");

    auto rgb_sub = node->create_subscription<sensor_msgs::msg::Image>(
        "/kinect2/qhd/image_raw", 1, CamRGBCallback);

    cv::namedWindow("RGB");

    rclcpp::spin(node);
    
    cv::destroyAllWindows();
    
    rclcpp::shutdown();

    return 0;
}