code: function ttfobject2symbol(ttf, options) {
  
              var xmlObject = {};
              var unitsPerEm = ttf.head.unitsPerEm;
              var descent = ttf.hhea.descent;
              // glyf 信息
              var symbolList = '';
              for (var i = 1, l = ttf.glyf.length; i < l; i++) {
                  var glyf = ttf.glyf[i];
                  // 筛选简单字形，并且有轮廓，有编码
                  if (!glyf.compound && glyf.contours) {
                      var contours = pathsUtil.flip(glyf.contours);
                      var glyfObject = {
                          descent: descent,
                          unitsPerEm: unitsPerEm,
                          id: getSymbolId(glyf, i),
                          d: contours2svg(contours)
                      };
                      symbolList += string.format(SYMBOL_TPL, glyfObject);
                  }
              }
              xmlObject.symbolList = symbolList;
  
              return string.format(XML_TPL, xmlObject);
          }
docs: ttf数据结构转svg
  
  @param {ttfObject} ttf ttfObject对象
  @param {Object} options 选项
  @param {Object} options.metadata 字体相关的信息
  @return {string} svg字符串