public static function GetWebImageMimeTypeByHeaderCode( string $file )
   {
      $f8b = File::ReadFirstBytes( $file, 8 );
      $ext = \strtolower( File::GetExtensionName( $file ) );
      switch ( $ext )
      {
         case 'gif':
            if ( static::HasGifHeader( $file, $f8b ) )
            {
               return 'image/gif';
            }
            return false;
         case 'jpg':
         case 'jpeg':
            if ( static::HasJpegHeader( $file, $f8b ) )
            {
               return 'image/jpeg';
            }
            return false;
         case 'png':
            if ( static::HasPngHeader( $file, $f8b ) )
            {
               return 'image/png';
            }
            return false;
         default:
            return false;
      }
   }