diff --git a/include/ws_functions/pwg.images.php b/include/ws_functions/pwg.images.php
index 09f3bbf0d..ef7286b9f 100644
--- a/include/ws_functions/pwg.images.php
+++ b/include/ws_functions/pwg.images.php
@@ -1446,6 +1446,294 @@ SELECT
   }
 }
 
+/**
+ * API method
+ * Adds a chunk of an image. Chunks don't have to be uploaded in the right sort order. When the last chunk is added, they get merged.
+ * @since 11
+ * @param mixed[] $params
+ *    @option string username
+ *    @option string password
+ *    @option chunk int number of the chunk
+ *    @option string chunk_sum MD5 sum of the chunk
+ *    @option chunks int total number of chunks for this image
+ *    @option string original_sum MD5 sum of the final image
+ *    @option int[] category
+ *    @option string filename
+ *    @option string name (optional)
+ *    @option string author (optional)
+ *    @option string comment (optional)
+ *    @option string date_creation (optional)
+ *    @option int level
+ *    @option string tag_ids (optional) - "tag_id,tag_id"
+ *    @option int image_id (optional)
+ */
+function ws_images_uploadAsync($params, &$service)
+{
+  global $conf, $user, $logger;
+
+  // additional check for some parameters
+  if (!preg_match('/^[a-fA-F0-9]{32}$/', $params['original_sum']))
+  {
+    return new PwgError(WS_ERR_INVALID_PARAM, 'Invalid original_sum');
+  }
+
+  if (!try_log_user($params['username'], $params['password'], false))
+  {
+    return new PwgError(999, 'Invalid username/password');
+  }
+
+  // build $user
+  // include(PHPWG_ROOT_PATH.'include/user.inc.php');
+  $user = build_user($user['id'], false);
+
+  if (!is_admin())
+  {
+    return new PwgError(401, 'Admin status is required.');
+  }
+
+  if ($params['image_id'] > 0)
+  {
+    $query='
+SELECT COUNT(*)
+  FROM '. IMAGES_TABLE .'
+  WHERE id = '. $params['image_id'] .'
+;';
+    list($count) = pwg_db_fetch_row(pwg_query($query));
+    if ($count == 0)
+    {
+      return new PwgError(404, __FUNCTION__.' : image_id not found');
+    }
+  }
+
+  // handle upload error as in ws_images_addSimple
+  // if (isset($_FILES['image']['error']) && $_FILES['image']['error'] != 0)
+
+  $output_filepath_prefix = $conf['upload_dir'].'/buffer/'.$params['original_sum'].'-u'.$user['id'];
+  $chunkfile_path_pattern = $output_filepath_prefix.'-%03uof%03u.chunk';
+
+  $chunkfile_path = sprintf($chunkfile_path_pattern, $params['chunk']+1, $params['chunks']);
+
+  // create the upload directory tree if not exists
+  if (!mkgetdir(dirname($chunkfile_path), MKGETDIR_DEFAULT&~MKGETDIR_DIE_ON_ERROR))
+  {
+    return new PwgError(500, 'error during buffer directory creation');
+  }
+  secure_directory(dirname($chunkfile_path));
+
+  // move uploaded file
+  move_uploaded_file($_FILES['file']['tmp_name'], $chunkfile_path);
+  $logger->debug(__FUNCTION__.' uploaded '.$chunkfile_path);
+
+  // MD5 checksum
+  $chunk_md5 = md5_file($chunkfile_path);
+  if ($chunk_md5 != $params['chunk_sum'])
+  {
+    unlink($chunkfile_path);
+    $logger->error(__FUNCTION__.' '.$chunkfile_path.' MD5 checksum mismatched');
+    return new PwgError(500, "MD5 checksum chunk file mismatched");
+  }
+
+  // are all chunks uploaded?
+  $chunk_ids_uploaded = array();
+  for ($i = 1; $i <= $params['chunks']; $i++)
+  {
+    $chunkfile = sprintf($chunkfile_path_pattern, $i, $params['chunks']);
+    if ( file_exists($chunkfile) && ($fp = fopen($chunkfile, "rb"))!==false )
+    {
+      $chunk_ids_uploaded[] = $i;
+      fclose($fp);
+    }
+  }
+
+  if ($params['chunks'] != count($chunk_ids_uploaded))
+  {
+    // all chunks are not yet available
+    $logger->debug(__FUNCTION__.' all chunks are not uploaded yet, maybe on next chunk, exit for now');
+    return array('message' => 'chunks uploaded = '.implode(',', $chunk_ids_uploaded));
+  }
+  
+  // all chunks available
+  $logger->debug(__FUNCTION__.' '.$params['original_sum'].' '.$params['chunks'].' chunks available, try now to get lock for merging');
+  $output_filepath = $output_filepath_prefix.'.merged';
+  
+  // chunks already being merged?
+  if ( file_exists($output_filepath) && ($fp = fopen($output_filepath, "rb"))!==false )
+  {
+    // merge file already exists
+    fclose($fp);
+    $logger->error(__FUNCTION__.' '.$output_filepath.' already exists, another merge is under process');
+    return array('message' => 'chunks uploaded = '.implode(',', $chunk_ids_uploaded));
+  }
+  
+  // create merged and open it for writing only
+  $fp = fopen($output_filepath, "wb");
+  if ( !$fp )
+  {
+    // unable to create file and open it for writing only
+    $logger->error(__FUNCTION__.' '.$chunkfile_path.' unable to create merge file');
+    return new PwgError(500, 'error while creating merged '.$chunkfile_path);
+  }
+
+  // acquire an exclusive lock and keep it until merge completes
+  // this postpones another uploadAsync task running in another thread
+  if (!flock($fp, LOCK_EX))
+  {
+    // unable to obtain lock
+    fclose($fp);
+    $logger->error(__FUNCTION__.' '.$chunkfile_path.' unable to obtain lock');
+    return new PwgError(500, 'error while locking merged '.$chunkfile_path);
+  }
+
+  $logger->debug(__FUNCTION__.' lock obtained to merge chunks');
+
+  // loop over all chunks
+  foreach ($chunk_ids_uploaded as $chunk_id)
+  {
+    $chunkfile_path = sprintf($chunkfile_path_pattern, $chunk_id, $params['chunks']);
+
+    // chunk deleted by preceding merge?
+    if (!file_exists($chunkfile_path))
+    {
+      // cancel merge
+      $logger->error(__FUNCTION__.' '.$chunkfile_path.' already merged');
+      flock($fp, LOCK_UN);
+      fclose($fp);
+      return array('message' => 'chunks uploaded = '.implode(',', $chunk_ids_uploaded));
+    }
+
+    if (!fwrite($fp, file_get_contents($chunkfile_path)))
+    {
+      // could not append chunk
+      $logger->error(__FUNCTION__.' error merging chunk '.$chunkfile_path);
+      flock($fp, LOCK_UN);
+      fclose($fp);
+
+      // delete merge file without returning an error
+      @unlink($output_filepath);
+      return new PwgError(500, 'error while merging chunk '.$chunk_id);
+    }
+
+    $logger->debug(__FUNCTION__.' original_sum='.$params['original_sum'].', chunk '.$chunk_id.'/'.$params['chunks'].' merged');
+
+    // delete chunk and clear cache
+    unlink($chunkfile_path);
+  }
+
+  // flush output before releasing lock
+  fflush($fp);
+  flock($fp, LOCK_UN);
+  fclose($fp);
+
+  $logger->debug(__FUNCTION__.' merged file '.$output_filepath.' saved');
+  
+  // MD5 checksum
+  $merged_md5 = md5_file($output_filepath);
+
+  if ($merged_md5 != $params['original_sum'])
+  {
+    unlink($output_filepath);
+    $logger->error(__FUNCTION__.' '.$output_filepath.' MD5 checksum mismatched!');
+    return new PwgError(500, "MD5 checksum merged file mismatched");
+  }
+
+  $logger->debug(__FUNCTION__.' '.$output_filepath.' MD5 checksum OK');
+
+  include_once(PHPWG_ROOT_PATH.'admin/include/functions_upload.inc.php');
+
+  $image_id = add_uploaded_file(
+    $output_filepath,
+    $params['filename'],
+    $params['category'],
+    $params['level'],
+    $params['image_id'],
+    $params['original_sum']
+  );
+
+  $logger->debug(__FUNCTION__.' image_id after add_uploaded_file = '.$image_id);
+
+  // and now, let's create tag associations
+  if (isset($params['tag_ids']) and !empty($params['tag_ids']))
+  {
+    set_tags(
+      explode(',', $params['tag_ids']),
+      $image_id
+    );
+  }
+
+  // time to set other infos
+  $info_columns = array(
+    'name',
+    'author',
+    'comment',
+    'date_creation',
+  );
+
+  $update = array();
+  foreach ($info_columns as $key)
+  {
+    if (isset($params[$key]))
+    {
+      $update[$key] = $params[$key];
+    }
+  }
+
+  if (count(array_keys($update)) > 0)
+  {
+    single_update(
+      IMAGES_TABLE,
+      $update,
+      array('id' => $image_id)
+    );
+  }
+
+  // final step, reset user cache
+  invalidate_user_cache();
+
+  // trick to bypass get_sql_condition_FandF
+  if (!empty($params['level']) and $params['level'] > $user['level'])
+  {
+    // this will not persist
+    $user['level'] = $params['level'];
+  }
+
+  // delete chunks older than a week
+  $now = time();
+  foreach (glob($conf['upload_dir'].'/buffer/'."*.chunk") as $file)
+  {
+    if (is_file($file))
+    {
+      if ($now - filemtime($file) >= 60 * 60 * 24 * 7) // 7 days
+      {
+        $logger->info(__FUNCTION__.' delete '.$file);
+        unlink($file);
+      }
+      else
+      {
+        $logger->debug(__FUNCTION__.' keep '.$file);
+      }
+    }
+  }
+
+  // delete merged older than a week
+  foreach (glob($conf['upload_dir'].'/buffer/'."*.merged") as $file)
+  {
+    if (is_file($file))
+    {
+      if ($now - filemtime($file) >= 60 * 60 * 24 * 7) // 7 days
+      {
+        $logger->info(__FUNCTION__.' delete '.$file);
+        unlink($file);
+      }
+      else
+      {
+        $logger->debug(__FUNCTION__.' keep '.$file);
+      }
+    }
+  }
+
+  return $service->invoke('pwg.images.getInfo', array('image_id' => $image_id));
+}
+
 /**
  * API method
  * Check if an image exists by it's name or md5 sum
diff --git a/ws.php b/ws.php
index 627e0cd98..bceda3a04 100644
--- a/ws.php
+++ b/ws.php
@@ -485,6 +485,36 @@ function ws_addDefaultMethods( $arr )
       $ws_functions_root . 'pwg.images.php',
       array('admin_only'=>true, 'post_only'=>true)
     );
+
+  $service->addMethod(
+    'pwg.images.uploadAsync',
+    'ws_images_uploadAsync',
+    array(
+        'username' => array(),
+        'password' => array('default'=>null),
+        'chunk' => array('type'=>WS_TYPE_INT|WS_TYPE_POSITIVE),
+        'chunk_sum' => array(),
+        'chunks' => array('type'=>WS_TYPE_INT|WS_TYPE_POSITIVE),
+        'original_sum' => array(),
+        'category' => array('default'=>null, 'flags'=>WS_PARAM_FORCE_ARRAY, 'type'=>WS_TYPE_ID),
+        'filename' => array(),
+        'name' => array('default'=>null),
+        'author' => array('default'=>null),
+        'comment' => array('default'=>null),
+        'date_creation' => array('default'=>null),
+        'level' => array('default'=>0, 'maxValue'=>max($conf['available_permission_levels']), 'type'=>WS_TYPE_INT|WS_TYPE_POSITIVE),
+        'tag_ids' => array('default'=>null, 'info'=>'Comma separated ids'),
+        'image_id' => array('default'=>null, 'type'=>WS_TYPE_ID),
+    ),
+    'Upload photo by chunks in a random order.
+<br>Use the <b>$_FILES[file]</b> field for uploading file.
+<br>Start with chunk 0 (zero).
+<br>Set the form encoding to "form-data".
+<br>You can update an existing photo if you define an existing image_id.
+<br>Requires <b>admin</b> credentials.',
+      $ws_functions_root . 'pwg.images.php',
+      array('post_only'=>true)
+    );
   
   $service->addMethod(
       'pwg.images.delete',