cvMatBuff = cvEncodeImage(".jpg", py, 0);
/* Fill in the file upload field from buffer */
curl_formadd(&formpost,
           &lastptr,
           CURLFORM_COPYNAME, "file",
           CURLFORM_BUFFER, "nowy.jpg",
           CURLFORM_BUFFERPTR, cvMatBuff,
           CURLFORM_END);
curl = curl_easy_init();

192.168.0.16 - - [17/Nov/2013 21:02:22] "POST /faces HTTP/1.1" 500 -
----------------------------------------
Exception happened during processing of request from ('192.168.0.16', 48537)
Traceback (most recent call last):
  File "/usr/lib/python2.7/SocketServer.py", line 295, in _handle_request_noblock
    self.process_request(request, client_address)
  File "/usr/lib/python2.7/SocketServer.py", line 321, in process_request
    self.finish_request(request, client_address)
  File "/usr/lib/python2.7/SocketServer.py", line 334, in finish_request
    self.RequestHandlerClass(request, client_address, self)
  File "/usr/lib/python2.7/SocketServer.py", line 649, in __init__
    self.handle()
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/serving.py", line 200, in handle
    rv = BaseHTTPRequestHandler.handle(self)
  File "/usr/lib/python2.7/BaseHTTPServer.py", line 340, in handle
    self.handle_one_request()
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/serving.py", line 235, in handle_one_request
    return self.run_wsgi()
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/serving.py", line 194, in run_wsgi
    traceback.plaintext)
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/utils.py", line 71, in __get__
    value = self.func(obj)
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/debug/tbtools.py", line 359, in plaintext
    return u'n'.join(self.generate_plaintext_traceback())
  File "/home/usr/flask/lib/python2.7/site-packages/werkzeug/debug/tbtools.py", line 353, in generate_plaintext_traceback
    frame.function_name
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc5 in position 17: ordinal not in range(128)

curl -F "file=@./medium.jpg" http://localhost:5000/faces

#include <stdio.h>
#include <curl/curl.h>
#include <sys/stat.h>
#include <fcntl.h>

int main(void)
{
  CURL *curl;
  CURLcode res;
  struct stat file_info;
  double speed_upload, total_time;
  FILE *fd;

  fd = fopen("debugit", "rb"); /* open file to upload */
  if(!fd) {

    return 1; /* can't continue */
  }

  /* to get the file size */
  if(fstat(fileno(fd), &file_info) != 0) {

    return 1; /* can't continue */
  }

  curl = curl_easy_init();
  if(curl) {
    /* upload to this place */
    curl_easy_setopt(curl, CURLOPT_URL,
                     "file:///home/dast/src/curl/debug/new");

    /* tell it to "upload" to the URL */
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);

    /* set where to read from (on Windows you need to use READFUNCTION too) */
    curl_easy_setopt(curl, CURLOPT_READDATA, fd);

    /* and give the size of the upload (optional) */
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE,
                     (curl_off_t)file_info.st_size);

    /* enable verbose for easier tracing */
    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

    res = curl_easy_perform(curl);
    /* Check for errors */
    if(res != CURLE_OK) {
      fprintf(stderr, "curl_easy_perform() failed: %sn",
              curl_easy_strerror(res));

    }
    else {
      /* now extract transfer info */
      curl_easy_getinfo(curl, CURLINFO_SPEED_UPLOAD, &speed_upload);
      curl_easy_getinfo(curl, CURLINFO_TOTAL_TIME, &total_time);

      fprintf(stderr, "Speed: %.3f bytes/sec during %.3f secondsn",
              speed_upload, total_time);

    }
    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  return 0;
}

sudo apt-get install language-pack-en

$ locale -a | grep "^en_.+UTF-8"
en_GB.UTF-8
en_US.UTF-8
$ export LC_ALL=en_GB.UTF-8
$ export LANG=en_GB.UTF-8