https://blog.wongcw.com/2018/12/21/%e8%b0%b7%e6%ad%8c%e6%82%84%e7%84%b6%e4%b8%8a%e7%b7%9achrome-canvas%e5%a1%97%e9%b4%89pwa%e6%87%89%e7%94%a8/