可扩展的书写用白板，不依赖任何第三方库。
Extensible whiteboard for writing with minimal reliance on third-party libraries.
DEMO：https://writeboard.gim.ink/
npm install --save writeboard
import { WhiteBoard } from 'writeboard'
const whiteBoardWidth = 500;
const whiteBoardHeight = 500;
/**
* @type {HTMLCanvasElement}
*/
const onscreenCanvas = document.getElementById("on-screen-canvas");
onscreenCanvas.width = whiteBoardWidth;
onscreenCanvas.height = whiteBoardHeight;
/**
* @type {HTMLCanvasElement}
*/
const offscreenCanvas = document.createElement('canvas');
offscreenCanvas.width = onscreenCanvas.width;
offscreenCanvas.height = onscreenCanvas.height;
const factory = FactoryMgr.createFactory(FactoryEnum.Default);
const whiteboard = factory.newWhiteBoard({
onscreen: onscreenCanvas,
offscreenCanvas: offscreenCanvas
});