/**
  * @return array
  */
 public function convertToBase64()
 {
     $base64 = '';
     if (isset($_SERVER['CONTENT_LENGTH']) && (int) $_SERVER['CONTENT_LENGTH'] > min(Utils::iniGetBytes('post_max_size'), 1000000)) {
         return array('error' => 'File too large - max size is 1 MB');
     } else {
         $base64 .= 'data:' . FsUtils::getMimeType($this->resource['tmp_name']) . ';' . 'base64,' . base64_encode(file_get_contents($this->resource['tmp_name']));
         $oldFileSize = filesize($this->resource['tmp_name']);
         $newFileSize = strlen($base64);
         $sizeDiff = $newFileSize * 100 / $oldFileSize - 100;
         $diffPrefix = $sizeDiff < 0 ? '-' : '+';
         $sizeDiff = $diffPrefix . (string) round($sizeDiff, 1) . '%';
         $msg = basename($this->resource['name']) . ', ' . 'was ' . FsUtils::formatFileSize($oldFileSize) . ', ' . 'now ' . FsUtils::formatFileSize($newFileSize) . ' ' . '(' . $diffPrefix . (string) round($sizeDiff, 1) . '%, ' . 'about +30% is normal)';
         return array('success' => $msg, 'base64' => $base64);
     }
 }