Use libcurl to upload the image of Opencv Mat to the file server, based on two methods of post request and ftp protocol

基于post请求的

基于postThe method of request is mainly to upload to such as installednginx-upload-module的nginx服务器上,urlThe directory where the parameter passed file is located,底下的curl_formaddadd filename.
不过nginx-upload-modulewill not put the file filename,Instead, save it with the name 00000000xx这样的文件10digit-named files,Prevent upload file conflicts,需要你自己写php或pythonThe script moves the file to the correct location or renames it.
The design seems to make sense（Instead, provide a script for Blue Dog）.

size_t writer(char *data, size_t size, size_t nmemb, string *writerData) {
    
    if (writerData == nullptr)
        return 0;
    size_t len = size * nmemb;
    writerData->append(data, len);
    return len;
}

void postUpLoad(const cv::Mat &img, const char *url) {
    
    vector<uchar> vec_Img;

    vector<int> vecCompression_params;

    vecCompression_params.push_back(cv::IMWRITE_JPEG_QUALITY);
    vecCompression_params.push_back(90);
    imencode(".jpg", img, vec_Img, vecCompression_params);

    CURL *curl;
    CURLcode res;

    string buffer;

    struct curl_httppost *post = nullptr;
    struct curl_httppost *last = nullptr;

    curl = curl_easy_init();
    if (curl) {
    
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_POST, 1);
        struct curl_slist *chunk = nullptr;
        chunk = curl_slist_append(chunk, "Accept:");

        chunk = curl_slist_append(chunk, "Authorization: Token ");

        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, chunk);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, &buffer);


        curl_formadd(&post, &last,
                     CURLFORM_COPYNAME, "photo",
                     CURLFORM_BUFFER, "photo.jpg",
                     CURLFORM_BUFFERPTR, vec_Img.data(),
                     CURLFORM_BUFFERLENGTH, vec_Img.size(),
                     CURLFORM_CONTENTTYPE, "image/jpg",
                     CURLFORM_END);

        curl_easy_setopt(curl, CURLOPT_HTTPPOST, post);

        // curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, my_trace);

        curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
        //
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

        res = curl_easy_perform(curl);

        if (res != CURLE_OK)
            fprintf(stderr, "curl_easy_perform() failed: %s\n", curl_easy_strerror(res));

        curl_easy_cleanup(curl);
    }
}

基于ftp协议的

urlPass the file path directly,比如ftp://server.name/subdir/image.jpg

struct TmpStream {
    
    void *ptr;
    size_t last_num;
};

static size_t read_callback(void *ptr, size_t size, size_t nmemb, TmpStream *stream) {
    
    if (stream->last_num <= 0)
        return 0;
    size_t retcode = size * nmemb;
    retcode = MIN(retcode, stream->last_num);
    memcpy(ptr, stream->ptr, retcode);
    stream->last_num -= retcode;
// curl_off_t nread = (curl_off_t) retcode;
// fprintf(stderr, " We read %" CURL_FORMAT_CURL_OFF_T
// " bytes from file\n", nread);
    return retcode;
}

void ftpUpload(const cv::Mat &img, const char *url) {
    
    vector<uchar> vec_Img;

    vector<int> vecCompression_params;

    vecCompression_params.push_back(cv::IMWRITE_JPEG_QUALITY);
    vecCompression_params.push_back(90);
    imencode(".jpg", img, vec_Img, vecCompression_params);

    // struct curl_slist *headerlist = nullptr;

    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();

    if (curl) {
    
        curl_easy_setopt(curl, CURLOPT_USERPWD, "smc:123456");
        /* we want to use our own write function */
        // curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);
        /* we want to use our own read function */
        curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_callback);

        /**create missing dir**/
        curl_easy_setopt(curl, CURLOPT_FTP_CREATE_MISSING_DIRS, 1L);

        /* enable uploading */
        curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

        /* specify target */
        curl_easy_setopt(curl, CURLOPT_URL, url);

        // /* pass in that last of FTP commands to run after the transfer */
        // curl_easy_setopt(curl, CURLOPT_POSTQUOTE, headerlist);

        /* now specify which file to upload */
        TmpStream stream = {
    vec_Img.data(), vec_Img.size()};
        curl_easy_setopt(curl, CURLOPT_READDATA, &stream);

        /* Set the size of the file to upload (optional). If you give a *_LARGE option you MUST make sure that the type of the passed-in argument is a curl_off_t. If you use CURLOPT_INFILESIZE (without _LARGE) you must make sure that to pass in a type 'long' argument. */
        curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
                         (curl_off_t) vec_Img.size());
        /* Now run off and do what you have been told! */
        res = curl_easy_perform(curl);
        /* Check for errors */
        if (res != CURLE_OK)
            fprintf(stderr, "curl_easy_perform() failed: %s\n",
                    curl_easy_strerror(res));

        /* clean up the FTP commands list */
        // curl_slist_free_all(headerlist);

        /* always cleanup */
        curl_easy_cleanup(curl);
    }
}