c++ - 如何将 boost.Asio 与 MJPEG 一起使用？-6ren

c++ - 如何将 boost.Asio 与 MJPEG 一起使用？

转载作者：塔克拉玛干更新时间：2023-11-03 02:22:17

我想实时将 OpenCV 图像(来自相机)广播到远程计算机，必须通过以太网来完成。图像在标准 OpenCV Mat 对象中连续接收。最终代码必须集成到 C++ (Qt) 应用程序中。

我找到了 this Python script这很好地完成了工作。

现在我试图获得该代码的 C++ 等价物，我设法使用 Boost Asio 和 Simple-Web-Server 创建了一个 HTTP 服务器。项目。我能够显示 static blue image/webcam 摄像头图像(未刷新)。

我写了一个代码，但它不工作。我的猜测是数据仅在函数返回时发送(永远不会返回)。如何在 while 循环的每次迭代后强制发送数据？

#include "server_http.hpp"

#include <thread>
#include <boost/chrono.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>
#include <boost/date_time/posix_time/posix_time_io.hpp>
#include <opencv2/opencv.hpp>
//#include <opencv/cv.h>

using namespace boost::posix_time;
typedef SimpleWeb::Server<SimpleWeb::HTTP> HttpServer;

cv::Mat image;
cv::VideoCapture cap;

int main()
{
  cap.open(0);
  if (!cap.isOpened ())
  {
    std::cerr << "Could not initialize capturing" << std::endl;
    return (-1);
  }
  cap >> image;

  HttpServer server(8080, 2);

  // Image resource is requested
  server.resource["^/cam.mjpg"]["GET"] =
      [=](HttpServer::Response& response, std::shared_ptr<HttpServer::Request> request)
      {
        time_facet *facet = new time_facet("%d-%b-%Y %H:%M:%S");
        std::cout.imbue(std::locale(std::cout.getloc(), facet));
        std::cout << second_clock::local_time() << " | " << "Camera image requested!" << std::endl;

        response <<
        "HTTP/1.1 200 OK\r\n"
        "Content-type: multipart/x-mixed-replace; boundary=--jpgboundary";
        //TODO: Send header

        while (1) // TODO: Allow exiting this
        {
          std::cout << "Send image" << std::endl;
          cap >> image;
          // Encode mat to jpg and copy it to content
          std::vector<uchar> buf;
          cv::imencode(".jpg", image, buf, std::vector<int>());
          std::string img_content(buf.begin(), buf.end());

          response << "--jpgboundary\r\n" << // Signal we start a new image
              "Content-type: image/jpeg" <<
              "Content-Length: " << img_content.length() << "\r\n" <<
              "\r\n" << img_content << "\r\n";
          std::this_thread::sleep_for(std::chrono::milliseconds(400));
        }
      };

  // Anything else is requested
  server.default_resource["GET"] = [](HttpServer::Response& response, std::shared_ptr<HttpServer::Request> request)
  {
    time_facet *facet = new time_facet("%d-%b-%Y %H:%M:%S");
    std::cout.imbue(std::locale(std::cout.getloc(), facet));
    std::cout << second_clock::local_time() << " | " << request->path << std::endl;

    std::string content =
    "<html><head></head><body>"
    "<img src=\"cam.mjpg\"/>"
    "</body></html>";
    response <<
    "HTTP/1.1 200 OK\r\n"
    "Content-Length: " << content.length() << "\r\n"
    "\r\n" << content;
  };

  std::thread server_thread([&server]()
  {
    server.start();
  });

  std::this_thread::sleep_for(std::chrono::seconds(1));
  server_thread.join();
  return 0;
}

编辑 1

根据 Technik Empire 的评论，我回到了 boost examples ;在 HTTP 服务器示例中，当回调返回时发送响应，所以我修改了回调以允许 do_write()套接字上的操作。

HTML 页面正确显示但图像不显示(而是显示损坏的图像图标)，我试图查看 Wireshark 会发生什么，但我不知道哪里出了问题。

这是我的 handle_request 函数:(request_handler.cpp):

void request_handler::handle_request(const request& req, reply& rep, connection &con)
{
  // Decode url to path.
  std::string request_path;
  if (!url_decode(req.uri, request_path))
  {
    rep = reply::stock_reply(reply::bad_request);
    return;
  }

  // Request path must be absolute and not contain "..".
  if (request_path.empty() || request_path[0] != '/'
      || request_path.find("..") != std::string::npos)
  {
    rep = reply::stock_reply(reply::bad_request);
    return;
  }

  // Determine the file extension.
  std::size_t last_slash_pos = request_path.find_last_of("/");
  std::string filename;
  if (last_slash_pos != std::string::npos)
    filename = request_path.substr(last_slash_pos + 1);

  if (filename == "cam.mjpg") // Image is requested
  {
    rep.status = reply::ok;
    rep.headers.resize(1);
    rep.headers[0].name = "Content-Type";
    rep.headers[0].value = "multipart/x-mixed-replace; boundary=--jpgboundary";
    rep.content.empty();
    con.do_write();
    rep.status = reply::none;

    while (true) // FIXME: How do I handle disconnection from the client?
    {
      cv::Mat image(200, 300, CV_8UC3);
      int random = rand() % 255 + 1;
      image = cv::Scalar(random, 0, 0); // Fill image with blue
      std::vector<uchar> buf;
      cv::imencode(".jpg", image, buf, std::vector<int>());
      std::string img_content(buf.begin(), buf.end());

      rep.headers.clear();
      rep.content.clear();

      rep.content.append("--jpgboundary\r\n");
      con.do_write();

      rep.content.clear();
      rep.headers.resize(2);
      rep.headers[0].name = "Content-Type";
      rep.headers[0].value = mime_types::extension_to_type("jpg");
      rep.headers[1].name = "Content-length";
      rep.headers[1].value = img_content.size();
      rep.content.append(img_content);
      rep.content.append("\r\n");
      con.do_write();

      boost::this_thread::sleep(boost::posix_time::milliseconds(500));
    }
  }
  else // Anything but the image is requested
  {
    std::string content =
    "<html><head></head><body>"
    "Hello :)<br>"
    "<img src=\"cam.mjpg\"/>"
    "</body></html>";

    rep.status = reply::ok;
    rep.headers.resize(2);
    rep.headers[0].name = "Content-Length";
    rep.headers[0].value = content.length();
    rep.headers[1].name = "Content-Type";
    rep.headers[1].value = mime_types::extension_to_type("html");
    rep.content.append(content);
    con.do_write();
    return;
  }
}

最佳答案

感谢 Firefox 网络分析器，我通过分析数据包让它工作，我复制了 Python header /内容答案并且它工作正常:

我添加了一个 reply::none 回复类型，并确保如果提供了此回复，则不会发送任何 HTTP 状态。所以在 reply::to_buffers() 函数中我添加了这个:

  if (status != none) // Don't add status to buffer if status is "none"
    buffers.push_back(status_strings::to_buffer(status));

request_handler.cpp 代码如下所示:

  if (filename == "cam.mjpg") // Image is requested
  {
    rep.status = reply::ok;
    rep.headers.resize(1);
    rep.headers[0].name = "Content-Type";
    rep.headers[0].value = "multipart/x-mixed-replace; boundary=--jpgboundary\r\n";
    con.do_write();

    while (true) // FIXME: How do I handle disconnection from the client?
    {
      cv::Mat image(200, 300, CV_8UC3);
      int random = rand() % 255 + 1;
      image = cv::Scalar(random, 0, 0); // Fill image with blue
      std::vector<uchar> buf;
      cv::imencode(".jpg", image, buf, std::vector<int>());
      std::string img_content(buf.begin(), buf.end());

      rep.status = reply::none;
      rep.headers.resize(0);
      rep.content.clear();
      rep.content.append("--jpgboundary");
      rep.content.append("\r\n");
      rep.content.append("Content-Type: image/jpeg");
      rep.content.append("\r\n");
      rep.content.append("Content-length: "+boost::lexical_cast<std::string>(img_content.length()));
      rep.content.append("\r\n");
      rep.content.append("\r\n");
      rep.content.append(img_content);
      rep.content.append("\r\n");
      con.do_write();
      boost::this_thread::sleep(boost::posix_time::milliseconds(100));
    }
  }
  else // Anything but the image is requested
  {
    std::string content =
    "<html><head></head><body>"
    "<img src=\"cam.mjpg\"/>"
    "</body></html>";

    rep.status = reply::ok;
    rep.headers.resize(2);
    rep.headers[0].name = "Content-Length";
    rep.headers[0].value = content.length();
    rep.headers[1].name = "Content-Type";
    rep.headers[1].value = mime_types::extension_to_type("html");
    rep.content.append(content);
    con.do_write();
    return;
  }