_caculateInnerPosition(outer, size) {
      const position = [];
      position[0] = outer[1];
      position[1] = outer[1] + size;
      position[2] = outer[1] + size * 2;
      position[3] = outer[2];

      return position;
    }
Calculate Inner Position
@param {Array} outer - outer position
@param {number} size - interval for calculate
@returns {Array} - inner position
@private