code: function cubic2Points(cubicList, contour) {
  
          var i;
          var l;
          var q2List = [];
  
          cubicList.forEach(function (c) {
              var list = bezierCubic2Q2(c[0], c[1], c[2], c[3]);
              for (i = 0, l = list.length; i < l; i++) {
                  q2List.push(list[i]);
              }
          });
  
          var q2;
          var prevq2;
          for (i = 0, l = q2List.length; i < l; i++) {
              q2 = q2List[i];
              if (i === 0) {
                  contour.push({
                      x: q2[1].x,
                      y: q2[1].y
                  });
                  contour.push({
                      x: q2[2].x,
                      y: q2[2].y,
                      onCurve: true
                  });
              }
              else {
                  prevq2 = q2List[i - 1];
                  // 检查是否存在切线点
                  if (
                      prevq2[1].x + q2[1].x === 2 * q2[0].x
                      && prevq2[1].y + q2[1].y === 2 * q2[0].y
                  ) {
                      contour.pop();
                  }
                  contour.push({
                      x: q2[1].x,
                      y: q2[1].y
                  });
                  contour.push({
                      x: q2[2].x,
                      y: q2[2].y,
                      onCurve: true
                  });
              }
          }
  
          contour.push({
              x: q2[2].x,
              y: q2[2].y,
              onCurve: true
          });
  
          return contour;
      }
docs: 三次贝塞尔曲线，转二次贝塞尔曲线
  
  @param {Array} cubicList 三次曲线数组
  @param {Array} contour 当前解析后的轮廓数组
  @return {Array} 当前解析后的轮廓数组