private void writeCommentExtension(OutputStream os) throws IOException {
		os.write('!');           /* GIF Extension Introducer */
		os.write(0xfe);          /* Comment Extension Label */

		int remainder = theComments.length() % 255;
		int nsubblocks_full = theComments.length() / 255;
		int nsubblocks = nsubblocks_full + (remainder > 0 ? 1 : 0);
		int ibyte = 0;
		for (int isb = 0; isb < nsubblocks; ++isb) {
			int size = isb < nsubblocks_full ? 255 : remainder;

			os.write(size);
			Gif89Put.ascii(theComments.substring(ibyte, ibyte + size), os);
			ibyte += size;
		}

		os.write(0);    /* block terminator */
	}