有ROS2中的网络摄像头发布存在小问题。

huangapple
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英文:

have little problem with webcam publish in ROS2

问题

I am currently your Chinese translator, I will only return the translated parts and avoid including any additional content. Here is the translation of your provided code:

这是发布者的代码：

  1. #include <chrono>
  2. #include <memory>
  3. #include "cv_bridge/cv_bridge.h"
  4. #include "rclcpp/rclcpp.hpp"
  5. #include "sensor_msgs/msg/image.hpp"
  6. #include "std_msgs/msg/header.hpp"
  7. #include <opencv2/opencv.hpp>
  8. #include <stdio.h>
  9. #include <opencv2/core/types.hpp>
  10. #include <opencv2/core/hal/interface.h>
  11. #include <image_transport/image_transport.hpp>
  12. #include <opencv2/imgproc/imgproc.hpp>
  14. using namespace std::chrono_literals;
  15. using namespace cv;
  17. class MinimalPublisher : public rclcpp::Node {
  18. public:
  19.     MinimalPublisher() : Node("minimal_publisher"), count_(0) {
  20.         auto qos_profile = rclcpp::QoS(rclcpp::KeepLast(10));
  21.         publisher_ = this->create_publisher<sensor_msgs::msg::Image>("topic", qos_profile);
  22.         timer_ = this->create_wall_timer(10ms, std::bind(&MinimalPublisher::timer_callback, this));
  23.     }
  25. private:
  26.     void timer_callback() {
  27.         cv_bridge::CvImagePtr cv_ptr;
  28.         cv::VideoCapture cap(0);
  29.         cv::Mat img(cv::Size(1280, 720), CV_8UC3);
  30.         cap >> img;
  31.         sensor_msgs::msg::Image::SharedPtr msg = cv_bridge::CvImage(std_msgs::msg::Header(), "bgr8", img).toImageMsg();
  32.         publisher_->publish(*msg);
  33.         RCLCPP_INFO(this->get_logger(), "publishing");
  34.     }
  36.     rclcpp::TimerBase::SharedPtr timer_;
  37.     rclcpp::Publisher<sensor_msgs::msg::Image>::SharedPtr publisher_;
  38.     size_t count_;
  39. };
  41. int main(int argc, char *argv[]) {
  42.     printf("Starting...");
  43.     rclcpp::init(argc, argv);
  44.     rclcpp::spin(std::make_shared<MinimalPublisher>());
  45.     rclcpp::shutdown();
  46.     return 0;
  47. }

订阅者的代码：

  1. #include <chrono>
  2. #include <memory>
  3. #include "cv_bridge/cv_bridge.h"
  4. #include "rclcpp/rclcpp.hpp"
  5. #include "sensor_msgs/msg/image.hpp"
  6. #include "std_msgs/msg/header.hpp"
  7. #include <opencv2/opencv.hpp>
  8. #include <opencv2/highgui.hpp>
  9. #include <stdio.h>
  10. #include <opencv2/core/types.hpp>
  11. #include <opencv2/core/hal/interface.h>
  12. #include <image_transport/image_transport.hpp>
  13. #include <opencv2/imgproc/imgproc.hpp>
  15. using std::placeholders::_1;
  17. class MinimalSubscriber : public rclcpp::Node {
  18. public:
  19.     MinimalSubscriber() : Node("minimal_subscriber") {
  20.         auto qos_profile = rclcpp::QoS(rclcpp::KeepLast(10));
  21.         subscription_ = this->create_subscription<sensor_msgs::msg::Image>(
  22.             "topic", qos_profile, std::bind(&MinimalSubscriber::topic_callback, this, _1));
  23.     }
  25. private:
  26.     void topic_callback(sensor_msgs::msg::Image::SharedPtr msg) const {
  27.         RCLCPP_INFO(this->get_logger(), "In callback");
  28.         cv_bridge::CvImagePtr cv_ptr;
  29.         cv_ptr = cv_bridge::toCvCopy(msg, "bgr8");
  30.         cv::imshow("minimal_subscriber", cv_ptr->image);
  31.         cv::waitKey(1);
  32.     }
  34.     rclcpp::Subscription<sensor_msgs::msg::Image>::SharedPtr subscription_;
  35. };
  37. int main(int argc, char *argv[]) {
  38.     rclcpp::init(argc, argv);
  39.     rclcpp::spin(std::make_shared<MinimalSubscriber>());
  40.     rclcpp::shutdown();
  41.     return 0;
  42. }

希望能帮到你，如果有其他需要翻译的，请随时告诉我。

英文:

I'm currently using Ubuntu 20.04, ROS2-foxy
what I'm trying to do is publish webcam image with using cv2, cv_bridge and subscribe it.
I successfully publish and subscribe the webcam but not in real-time.
publish node is publishing webcam every two seconds. which means publishing image like delayed image.
I tried to search and fix the problem but and can't make it so I need some help.
I will post my publisher and subscriber code down here.

This is publisher code.

  1. #include &lt;chrono&gt;
  2. #include &lt;memory&gt;
  3. #include &quot;cv_bridge/cv_bridge.h&quot;
  4. #include &quot;rclcpp/rclcpp.hpp&quot;
  5. #include &quot;sensor_msgs/msg/image.hpp&quot;
  6. #include &quot;std_msgs/msg/header.hpp&quot;
  7. #include &lt;opencv2/opencv.hpp&gt;
  8. #include &lt;stdio.h&gt;
  9. #include &lt;opencv2/core/types.hpp&gt;
  10. #include &lt;opencv2/core/hal/interface.h&gt;
  11. #include &lt;image_transport/image_transport.hpp&gt;
  12. #include &lt;opencv2/imgproc/imgproc.hpp&gt;
  14. using namespace std::chrono_literals;
  15. using namespace cv;
  17. class MinimalPublisher : public rclcpp::Node {
  19. public:
  21. MinimalPublisher() : Node(&quot;minimal_publisher&quot;), count_(0) {
  23.     auto qos_profile = rclcpp::QoS(rclcpp::KeepLast(10));
  24.     publisher_ = this-&gt;create_publisher&lt;sensor_msgs::msg::Image&gt;(&quot;topic&quot;, qos_profile);
  25.     timer_ = this-&gt;create_wall_timer(10ms, std::bind(&amp;MinimalPublisher::timer_callback, this));
  27. }
  29. private:
  31. void timer_callback() {
  33.     cv_bridge::CvImagePtr cv_ptr;
  34.     cv::VideoCapture cap(0);
  35.     cv::Mat img(cv::Size(1280, 720), CV_8UC3);
  36.     cap &gt;&gt; img;
  37.     sensor_msgs::msg::Image::SharedPtr msg = cv_bridge::CvImage(std_msgs::msg::Header(), &quot;bgr8&quot;, img).toImageMsg();      
  38.     publisher_-&gt;publish(*msg);
  39.     RCLCPP_INFO(this-&gt;get_logger(), &quot;publishing&quot;);
  40. }
  41.   rclcpp::TimerBase::SharedPtr timer_;
  42.   rclcpp::Publisher&lt;sensor_msgs::msg::Image&gt;::SharedPtr publisher_;
  43.   size_t count_; 
  44. };
  46. int main(int argc, char *argv[]) {
  48.   printf(&quot;Starting...&quot;);
  49.   rclcpp::init(argc, argv);
  50.   rclcpp::spin(std::make_shared&lt;MinimalPublisher&gt;());
  51.   rclcpp::shutdown();
  52.   return 0; 
  53. }

Subscriber code:

  1. #include &lt;chrono&gt;
  2. #include &lt;memory&gt;
  4. #include &quot;cv_bridge/cv_bridge.h&quot;
  5. #include &quot;rclcpp/rclcpp.hpp&quot;
  6. #include &quot;sensor_msgs/msg/image.hpp&quot;
  7. #include &quot;std_msgs/msg/header.hpp&quot;
  8. #include &lt;opencv2/opencv.hpp&gt;
  9. #include &lt;opencv2/highgui.hpp&gt;
  10. #include &lt;stdio.h&gt;
  12. #include &lt;opencv2/core/types.hpp&gt;
  13. #include &lt;opencv2/core/hal/interface.h&gt;
  14. #include &lt;image_transport/image_transport.hpp&gt;
  15. #include &lt;opencv2/imgproc/imgproc.hpp&gt;
  17. using std::placeholders::_1;
  19. class MinimalSubscriber : public rclcpp::Node {
  20.   public:
  21.     MinimalSubscriber()
  22.     : Node(&quot;minimal_subscriber&quot;)
  23.     {
  24.       auto qos_profile = rclcpp::QoS(rclcpp::KeepLast(10));
  25.       subscription_ = this-&gt;create_subscription&lt;sensor_msgs::msg::Image&gt;(
  26.       &quot;topic&quot;, qos_profile, std::bind(&amp;MinimalSubscriber::topic_callback, this, _1));
  27.     }
  29.   private :
  30.     void topic_callback(sensor_msgs::msg::Image::SharedPtr msg) const
  31.     {
  32.       RCLCPP_INFO(this-&gt;get_logger(), &quot;In callback&quot;);
  33.       cv_bridge::CvImagePtr cv_ptr;
  34.       cv_ptr = cv_bridge::toCvCopy(msg,&quot;bgr8&quot;);
  35.       cv::imshow(&quot;minimal_subscriber&quot;, cv_ptr-&gt;image);
  36.       cv::waitKey(1);
  37.     }
  38.     rclcpp::Subscription&lt;sensor_msgs::msg::Image&gt;::SharedPtr subscription_;
  39. };
  41. int main(int argc, char *argv[])
  42. {
  43.   rclcpp::init(argc, argv);
  44.   rclcpp::spin(std::make_shared&lt;MinimalSubscriber&gt;());
  45.   rclcpp::shutdown();
  46.   return 0;
  47. }

I want to see my webcam streaming working normally. I want this simple job happen in C++, cv_bridge, cv2.

答案1

得分: 1

每次调用timer_callback函数时，都会使用cv::VideoCapture cap(0);打开一个新的视频捕获流。视频流的打开和关闭导致了您正在经历的延迟问题。

已解决！

这是详细的代码：https://github.com/Robotisim/solving_ros_problems/commit/b099e5d787d91205225416953516813ba2dce7c3

英文:

Every time the timer_callback function is called, you're opening a new video capture stream with cv::VideoCapture cap(0);. The opening and closing of the video stream is be causing the delay you're experiencing.

Fixed it !

here is a detailed code : https://github.com/Robotisim/solving_ros_problems/commit/b099e5d787d91205225416953516813ba2dce7c3

huangapple
  • 本文由 发表于 2023年5月18日 12:37:05
  • 转载请务必保留本文链接：https://go.coder-hub.com/76277775.html
  • c++
  • opencv
  • python
  • ros
  • ros2
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