code: function gradient(colors) {
      var points = [];
      if (isString(colors)) {
        colors = colors.split('-');
      }
      each(colors, function (color) {
        if (color.indexOf('#') === -1) {
          color = ColorUtil.toRGB(color);
        }
        points.push(rgb2arr(color));
      });
      return function (percent) {
        return calColor(points, percent);
      };
    }
docs: 获取渐变函数
  @param  {Array} colors 多个颜色
  @return {String} 颜色值