Reading identification of instrument panel

 # include  <iostream>
 # include  <curl/curl.h>

 //Download link of libcurl library: https://curl.haxx.se/download.html
 //Download link of jsoncpp library: https://github.com/open-source-parsers/jsoncpp/
 const  static std :: string request_url =  " https://aip.baidubce.com/rest/2.0/ocr/v1/meter " ;
 static std :: string meter_result ;
 /** *The curl sends the callback function called by the http request. The returned body in json format is parsed in the callback function, and the parsing result is stored in the global static variable *See the libcurl document for @ param parameter definitions *@ return See the libcurl document for the definition of the return value */
 static size_t callback ( void  * ptr , size_t size , size_t nmemb ,  void  * stream )  {
     //The obtained body is stored in ptr and converted to string format first meter_result = std :: string ( ( char  * ) ptr , size * nmemb ) ;
     return size * nmemb ;
 }
 /** *Reading identification of instrument panel *@ return If the call is successful, 0 will be returned. If an error occurs, other error codes will be returned */
 int  meter ( std :: string & json_result ,  const std :: string & access_token )  { std :: string url = request_url +  "? access_token="  + access_token ; CURL * curl =  NULL ; CURLcode result_code ;
     int is_success ; curl =  curl_easy_init ( ) ;
     if  ( curl )  {
         curl_easy_setopt ( curl , CURLOPT_URL , url . data ( ) ) ;
         curl_easy_setopt ( curl , CURLOPT_POST ,  one ) ; curl_httppost * post =  NULL ; curl_httppost * last =  NULL ;
         curl_formadd ( & post ,  & last , CURLFORM_COPYNAME ,  "image" , CURLFORM_COPYCONTENTS ,  "【base64_img】" , CURLFORM_END ) ;

         curl_easy_setopt ( curl , CURLOPT_HTTPPOST , post ) ;
         curl_easy_setopt ( curl , CURLOPT_WRITEFUNCTION , callback ) ; result_code =  curl_easy_perform ( curl ) ;
         if  ( result_code != CURLE_OK )  {
             fprintf ( stderr ,  "curl_easy_perform() failed: %s\n" ,
                     curl_easy_strerror ( result_code ) ) ; is_success =  one ;
             return is_success ;
         } json_result = meter_result ;
         curl_easy_cleanup ( curl ) ; is_success =  zero ;
     }  else  {
         fprintf ( stderr ,  "curl_easy_init() failed." ) ; is_success =  one ;
     }
     return is_success ;
 }