align(onPts, offPts) {
    const xas = this.xAlign.map(group => group.map(expandAlign));
    const yas = this.yAlign.map(group => group.map(expandAlign));
    // Aligning
    xas.forEach(group => setCoordAvg('x', onPts, offPts, group));
    yas.forEach(group => setCoordAvg('y', onPts, offPts, group));
  }
Handle alignments of given on-points and off-points using `this.xAlign`
and `this.yAlign`.
@param { [number, number][] } onPts 
@param { [number, number][] } offPts