code: function interpolate(path) {
              var newPath = [];
              for (var i = 0, l = path.length; i < l; i++) {
                  var next = i === l - 1 ? 0 : i + 1;
                  newPath.push(path[i]);
                  // 插值
                  if (!path[i].onCurve && !path[next].onCurve) {
                      newPath.push({
                          x: (path[i].x + path[next].x) / 2,
                          y: (path[i].y + path[next].y) / 2,
                          onCurve: true
                      });
                  }
              }
  
              return newPath;
          }
docs: 对路径进行插值，补全省略的点
  
  @param {Array} path 路径
  @return {Array} 路径