標準 c++ 言語にはネットワーク関連処理を行うためのライブラリが脆弱ですので、本ページでは libcurl
というオープンソースライブラリを使用して機能を実現します。libcurlは複数のプラットフォームで同じようにビルド、稼動させることができるフリーで使いやすいクライアントサイド
URL 転送ライブラリです。Microsoft Visual Studio からも利用可能です。
C:\Users\foo\Documents\Github>cd vcpkg
C:\Users\foo\Documents\Github\vcpkg>bootstrap-vcpkg.bat
Downloading https://github.com/microsoft/vcpkg-tool/releases/download/2023-02-16/vcpkg.exe -> C:\Users\foo\Documents\Github\vcpkg\vcpkg.exe... done.
Validating signature... done.
Telemetry
---------
vcpkg collects usage data in order to help us improve your experience.
The data collected by Microsoft is anonymous.
You can opt-out of telemetry by re-running the bootstrap-vcpkg script with -disableMetrics,
passing --disable-metrics to vcpkg on the command line,
or by setting the VCPKG_DISABLE_METRICS environment variable.
Read more about vcpkg telemetry at docs/about/privacy.md
C:\Users\foo\Documents\Github\vcpkg>
triplet とは環境を表す文字列で、対応している triplet は vcpkg help
triplet コマンドで確認できます。
vcpkg install curl:x64-windows
[実行例]
C:\Users\foo\Documents\Github\vcpkg>vcpkg install curl:x64-windows
Computing installation plan...
The following packages will be built and installed:
curl[core,non-http,schannel,ssl,sspi]:x64-windows -> 7.88.1
* zlib[core]:x64-windows -> 1.2.13
Additional packages (*) will be modified to complete this operation.
Detecting compiler hash for triplet x64-windows...
Restored 0 package(s) from C:\Users\foo\AppData\Local\vcpkg\archives in 161 us. Use --debug to see more details.
Installing 1/2 zlib:x64-windows...
Building zlib[core]:x64-windows...
-- Using cached madler-zlib-v1.2.13.tar.gz.
*** 途中省略 ***
-- Fixing pkgconfig file: C:/Users/foo/Documents/Github/vcpkg/packages/curl_x64-windows/debug/lib/pkgconfig/libcurl.pc
-- Installing: C:/Users/foo/Documents/Github/vcpkg/packages/curl_x64-windows/share/curl/vcpkg-cmake-wrapper.cmake
-- Installing: C:/Users/foo/Documents/Github/vcpkg/packages/curl_x64-windows/share/curl/copyright
-- Performing post-build validation
Stored binary cache: "C:\Users\foo\AppData\Local\vcpkg\archives\0b\0be4e066bb110c9e83d7ab0d78d61cee202eb0797b927e196b1af2e37d0a65d4.zip"
Elapsed time to handle curl:x64-windows: 1.262 min
Total install time: 1.423 min
curl provides CMake targets:
# this is heuristically generated, and may not be correct
find_package(CURL CONFIG REQUIRED)
target_link_libraries(main PRIVATE CURL::libcurl)
C:\Users\foo\Documents\Github\vcpkg>
以上で libcurl のインストールを完了です。
(4) Visual Studio へ組み込む
vcpkg integrate install
コマンドを実行することで、vcpkgでインストールしたライブラリを Visual Studio
から利用できるようになります。インクルードディレクトリやライブラリディレクトリ、およびライブラリが自動で "Visual Studio"
に追加されます。
Visual Studio
環境へ組み込まれることを好まない場合、こちらのコマンドを実行せずにご自身で個別にプロジェクトへ
インクルードディレクトリやライブラリディレクトリ、およびライブラリの設定を行ってください。
vcpkg integrate install
[実行例]
C:\Users\foo\Documents\Github\vcpkg>vcpkg integrate install
Applied user-wide integration for this vcpkg root.
CMake projects should use: "-DCMAKE_TOOLCHAIN_FILE=C:/Users/foo/Documents/Github/vcpkg/scripts/buildsystems/vcpkg.cmake"
All MSBuild C++ projects can now #include any installed libraries. Linking will be handled automatically. Installing new libraries will make them instantly available.
C:\Users\foo\Documents\Github\vcpkg>
(5) インストールしたライブラリを確認
vcpkg list
コマンドを実行することで、インストールしたライブラリ一覧を表示することができます。
vcpkg list
[実行例]
C:\Users\foo\Documents\Github\vcpkg>vcpkg list
curl:x64-windows 7.88.1 A library for transferring data with URLs
curl[non-http]:x64-windows Enables protocols beyond HTTP/HTTPS/HTTP2
curl[schannel]:x64-windows SSL support (Secure Channel)
curl[ssl]:x64-windows Default SSL backend
curl[sspi]:x64-windows SSPI support
vcpkg-cmake-config:x64-windows 2022-02-06#1
vcpkg-cmake:x64-windows 2022-12-22
zlib:x64-windows 1.2.13 A compression library
zlib:x86-windows 1.2.13 A compression library
C:\Users\foo\Documents\Github\vcpkg>
/*
======================================================================================
[Abstract]
Try connecting to an i-PRO camera with JPEG.
HTTPで接続してJPEGの連続表示で i-PRO カメラと接続してみる
[Details]
Let's try first.
まずはやってみる
[Library install]
opencv: See "https://i-pro-corp.github.io/Programing-Items/cpp_vs/install_opencv.html"
libcurl: See "https://i-pro-corp.github.io/Programing-Items/cpp_vs/connect_camera/connect_with_jpeg.html"
======================================================================================
*/
#include <iostream>
#include <vector>
#include <opencv2/opencv.hpp>
#include <opencv2/core/utility.hpp>
#include <curl/curl.h>
const std::string user_id = "user-id"; // Change to match your camera setting
const std::string user_pw = "password"; // Change to match your camera setting
const std::string host = "192.168.0.10"; // Change to match your camera setting
const std::string resolution = "1920";
const std::string winname = "VIDEO"; // Window title
const std::string cameraURL = "http://" + host + "/cgi-bin/camera?resolution=" + resolution;
/// <summary>
/// A curl callback function. Call this function when data is received.
/// </summary>
/// <param name="ptr">ptr points to the delivered data.</param>
/// <param name="size">size is always 1.</param>
/// <param name="nmemb">the size of the deliverd data is nmemb.</param>
/// <param name="userdata">Pointer to buffer specified by CURLOPT_WRITEDATA</param>
/// <returns>
/// Return the number of bytes actually taken care of.
/// If that amount differs from the amount passed to your callback function, it will signal an error condition to the library.
/// This will cause the transfer to get aborted and the libcurl function used will return CURLE_WRITE_ERROR.
/// </returns>
/// <detail>See "https://curl.se/libcurl/c/CURLOPT_WRITEFUNCTION.html" for details.</detail>
size_t onReceive(void* ptr, size_t size, size_t nmemb, void* userdata) {
std::vector<char>* receiveBuffer = (std::vector<char>*)userdata;
const size_t sizes = size * nmemb;
receiveBuffer->insert(receiveBuffer->end(), (char*)ptr, (char*)ptr + sizes);
return sizes;
}
/// <summary>
/// Receiving one JPEG image from the i-PRO camera.
/// </summary>
/// <param name="url">CGI command for 1 shot JPEG</param>
/// <param name="receiveBuffer">A variable to store the received JPEG image</param>
/// <retval>true: Success to get JPEG image.</retval>
/// <retval>false: Failed to get JPEG image.</retval>
bool get_jpeg_image(const std::string url, std::vector<char>& receiveBuffer) {
CURL* curl = NULL;
CURLcode res;
// initialize curl.
curl = curl_easy_init();
if (!curl) {
printf("curl_easy_init() failed...\n");
return false;
}
// curl option for digest authentication
curl_easy_setopt(curl, CURLOPT_HTTPAUTH, CURLAUTH_DIGEST);
std::string user_id_pw = user_id + ":" + user_pw;
curl_easy_setopt(curl, CURLOPT_USERPWD, user_id_pw.c_str());
// curl option
curl_easy_setopt(curl, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &receiveBuffer);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, onReceive);
// execute
res = curl_easy_perform(curl);
if (res != CURLE_OK) {
printf("curl_easy_perform() failed...%s\n", curl_easy_strerror(res));
return false;
}
curl_easy_cleanup(curl);
return true;
}
/// <summary>
/// main function
/// </summary>
/// <returns>Always returns EXIT_SUCCESS(0).</returns>
int main() {
cv::Mat recv_data;
bool isDataReceived;
char ret;
std::vector<char> receiveBuffer;
while (true) {
// get image data by HTTP
isDataReceived = get_jpeg_image(cameraURL, receiveBuffer);
if (!isDataReceived) {
std::cout << "get_jpeg_image() failed..." << std::endl;
break;
}
// JPEG decode
cv::Mat frame = cv::imdecode(receiveBuffer, cv::IMREAD_UNCHANGED);
// Clear all received data.
receiveBuffer.clear();
// Please modify the value to fit your PC screen size.
resize(frame, frame, cv::Size(), 0.5, 0.5); // Setting by magnification.
// Display video.
cv::imshow(winname, frame);
ret = (char)cv::waitKey(1); // necessary to display the video by cv::imshow().
// Press the "q" key to finish.
if (ret == 'q') {
break;
}
}
cv::destroyAllWindows();
return EXIT_SUCCESS;
}
Licensed under the Apache License, Version
2.0 (the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
Unless required by
applicable law or agreed to in writing, software distributed under the
License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied. See the License for
the specific language governing permissions and limitations under the
License.
