public function ValidateUpload($InputName, $ThrowError = TRUE) {
   
      if (!function_exists('gd_info'))
         throw new Exception(T('The uploaded file could not be processed because GD is not installed.'));
   
      // Make sure that all standard file upload checks are performed.
      $TmpFileName = parent::ValidateUpload($InputName, $ThrowError);
      
      // Now perform image-specific checks.
      if ($TmpFileName) {
         $Size = getimagesize($TmpFileName);
         if ($Size === FALSE)
            throw new Exception(T('The uploaded file was not an image.'));
      }
      
      return $TmpFileName;
   }