protected SFont toZssFont(Font poiFont) {
    if (poiFont == null) return null; // ZSS-1138

    SFont font = null;
    final short fontIndex = poiFont.getIndex();
    if (importedFont.containsKey(fontIndex)) {
      font = importedFont.get(fontIndex);
    } else {
      font = createZssFont(poiFont);
      importedFont.put(fontIndex, font); // ZSS-677
    }
    return font;
  }
  protected SFont createZssFont(Font poiFont) {
    SFont font = book.createFont(true);
    // font
    font.setName(poiFont.getFontName());
    font.setBoldweight(PoiEnumConversion.toBoldweight(poiFont.getBoldweight()));
    font.setItalic(poiFont.getItalic());
    font.setStrikeout(poiFont.getStrikeout());
    font.setUnderline(PoiEnumConversion.toUnderline(poiFont.getUnderline()));

    font.setHeightPoints(poiFont.getFontHeightInPoints());
    font.setTypeOffset(PoiEnumConversion.toTypeOffset(poiFont.getTypeOffset()));
    font.setColor(book.createColor(BookHelper.getFontHTMLColor(workbook, poiFont)));

    return font;
  }