{"id":28756836,"url":"https://github.com/wx-chevalier/web-whiteboard","last_synced_at":"2025-06-17T03:08:55.040Z","repository":{"id":38410388,"uuid":"198856762","full_name":"wx-chevalier/web-whiteboard","owner":"wx-chevalier","description":"Online web  annotation tools \u0026 whiteboard(both live, playback, and collaborative mode)  for real-time visual collaboration, in business and education. | 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web-whiteboard\n\nWeb whiteboard screencasting(both live and playback mode) with background slides, can be used as a graphics tablet for online tutoring or remote collaboration.\n\n![](https://i.postimg.cc/pXNpNRwq/image.png)\n\n在很多培训、协作、在线演讲的场景下，我们需要有电子白板的功能，能够方便地在演讲者与听众之间共享屏幕、绘制等信息。[fc-whiteboard https://parg.co/NiK](https://github.com/wx-chevalier/fractal-components/tree/master/fc-whiteboard) 是 Web 在线白板组件库，支持实时直播（一对多）与回放两种模式，其绘制版也能够独立使用。fc-whiteboard 内置了 EventHub，只需要像 [Mushi-Chat](https://github.com/wx-chevalier/Mushi-Chat) 这样提供简单的 WebSocket 服务端，即可快速构建实时在线共享电子白板。\n\nweb-whiteboard 是 [fractal-components](https://github.com/wx-chevalier/fractal-components) 项目的一部分，其使用的项目模板源自 [m-fe-rtw](https://github.com/wx-chevalier/m-fe-rtw)。\n\n# Usage | 使用\n\n## Whiteboard live mode | 直播模式\n\n直播模式的效果如下图所示：\n\n![](https://i.postimg.cc/65t7MNBQ/Kapture-2019-04-17-at-13-47-52.gif)\n\nSource code can be found in [Code Sandbox](https://codesandbox.io/s/3q1z35q53p?fontsize=14) or [Demo](https://codesandbox.io/s/3q1z35q53p?fontsize=14);\n\n源代码请参考 [Code Sandbox](https://codesandbox.io/s/3q1z35q53p?fontsize=14) or [Demo](https://codesandbox.io/s/3q1z35q53p?fontsize=14);\n\n```ts\nimport { EventHub, Whiteboard, MirrorWhiteboard } from '@m-fe/whiteboard';\n\n// 构建消息中间件\nconst eventHub = new EventHub();\n\neventHub.on('sync', (changeEv: SyncEvent) =\u003e {\n  console.log(changeEv);\n});\n\nconst images = [\n  'https://upload-images.jianshu.io/upload_images/1647496-6bede989c09af527.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240',\n  'http://upload-images.jianshu.io/upload_images/1647496-d281090a702045e5.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240',\n  'http://upload-images.jianshu.io/upload_images/1647496-611a416be07d7ca3.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240',\n];\n\n// 初始化演讲者端\nconst whiteboard = new Whiteboard(\n  document.getElementById('root') as HTMLDivElement,\n  {\n    sources: images,\n    eventHub,\n    // Enable this option to disable incremental sync, just use full sync\n    onlyEmitSnap: false,\n  },\n);\n\nwhiteboard.open();\n\n// 初始化镜像端，即观众端\nconst mirrorWhiteboard = new MirrorWhiteboard(\n  document.getElementById('root-mirror') as HTMLDivElement,\n  {\n    sources: images,\n    eventHub,\n  },\n);\n\nmirrorWhiteboard.open();\n```\n\n## WebSocket 集成\n\nWebSocket 天然就是以事件驱动的消息通信，fc-whiteboard 内部对于消息有比较好的封装，我们建议使用者直接将消息透传即可：\n\n```js\nconst wsEventHub = new EventEmitter();\n\nif (isPresenter) {\n  wsEventHub.on('sync', data =\u003e {\n    if (data.event === 'finish') {\n      // 单独处理结束事件\n      if (typeof callback === 'function') {\n        callback();\n      }\n    }\n    const msg = {\n      from: `${currentUser.id}`,\n      type: 'room',\n      to: `${chatroom.room_id}`,\n      msg: {\n        type: 'cmd',\n        action: 'whiteboard/sync',\n        message: JSON.stringify(data),\n      },\n    };\n    socket.sendMessage(msg);\n  });\n} else {\n  socket.onMessage(([data]) =\u003e {\n    const {\n      msg: { type, message },\n    } = data;\n\n    if (type === 'whiteboard/sync') {\n      wsEventHub.emit('sync', JSON.parse(message));\n    }\n  });\n}\n```\n\n## Whiteboard replay mode | 回放模式\n\nfc-whiteboard 还支持回访模式，即我们可以将某次白板操作录制下来，可以一次性或者分批将事件传递给 ReplayWhiteboard，它就会按序播放：\n\n```ts\nimport { ReplayWhiteboard } from '@m-fe/whiteboard';\nimport * as events from './events.json';\n\nlet hasSend = false;\n\nconst whiteboard = new ReplayWhiteboard(\n  document.getElementById('root') as HTMLDivElement,\n);\n\nwhiteboard.setContext(events[0].timestamp, async (t1, t2) =\u003e {\n  if (!hasSend) {\n    hasSend = true;\n    return events as any;\n  }\n\n  return [];\n});\n\nwhiteboard.open();\n```\n\nThe persistent events are listed as follow:\n\n事件的基本结构如下所示，具体的事件类别我们会在下文介绍：\n\n```json\n[\n  {\n    \"event\": \"borderSnap\",\n    \"id\": \"08e65660-6064-11e9-be21-fb33250b411f\",\n    \"target\": \"whiteboard\",\n    \"border\": {\n      \"id\": \"08e65660-6064-11e9-be21-fb33250b411f\",\n      \"sources\": [\n        \"https://upload-images.jianshu.io/upload_images/1647496-6bede989c09af527.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240\",\n        \"http://upload-images.jianshu.io/upload_images/1647496-d281090a702045e5.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240\",\n        \"http://upload-images.jianshu.io/upload_images/1647496-611a416be07d7ca3.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240\"\n      ],\n      \"pageIds\": [\n        \"08e65661-6064-11e9-be21-fb33250b411f\",\n        \"08e6a480-6064-11e9-be21-fb33250b411f\",\n        \"08e6cb91-6064-11e9-be21-fb33250b411f\"\n      ],\n      \"visiblePageIndex\": 0,\n      \"pages\": [\n        { \"id\": \"08e65661-6064-11e9-be21-fb33250b411f\", \"markers\": [] },\n        { \"id\": \"08e6a480-6064-11e9-be21-fb33250b411f\", \"markers\": [] },\n        { \"id\": \"08e6cb91-6064-11e9-be21-fb33250b411f\", \"markers\": [] }\n      ]\n    },\n    \"timestamp\": 1555431837\n  }\n  ...\n]\n```\n\n## Use drawboard alone | 单独使用 Drawboard\n\nDrawboard 也可以单独使用作为画板，整体可以被导出为图片：\n\n```html\n\u003cimg id=\"root\" src=\"https://upload-images.jianshu.io/upload_images/1647496-6bede989c09af527.jpg?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240\"\u003e\u003c/img\u003e\n```\n\n```ts\nimport { Drawboard } from '@m-fe/whiteboard';\n\nconst d = new Drawboard({\n  imgEle: document.getElementById('root') as HTMLImageElement,\n});\n\nd.open();\n```\n\n# 内部设计\n\nfc-whiteboard 的内部组件级别，依次是 WhiteBoard, WhitePage, Drawboard 与 Marker，本节即介绍内部设计与实现。\n\n![](https://i.postimg.cc/NjwLZ9Gf/image.png)\n\n## Draw System | 绘制系统\n\n绘制能力最初改造自 [markerjs](https://markerjs.com/)，在 Drawboard 中提供了基础的画板，即 boardCanvas 与 boardHolder，后续的所有 Marker 即挂载于 boardCanvas 中，并相对于其进行绝对定位。当我们添加某个 Marker，即执行以下步骤：\n\n```ts\nconst marker = markerType.createMarker(this.page);\n\nthis.markers.push(marker);\nthis.selectMarker(marker);\nthis.boardCanvas.appendChild(marker.visual);\n\n// 定位\nmarker.moveTo(x, y);\n```\n\n目前 fc-whiteboard 中内置了 ArrowMarker, CoverMarker, HighlightMarker, LineMarker, TextMarker 等多种 Marker：\n\n```ts\nexport class BaseMarker extends DomEventAware {\n  id: string = uuid();\n  type: MarkerType = 'base';\n  // 归属的 WhitePage\n  page?: WhitePage;\n  // 归属的 Drawboard\n  drawboard?: Drawboard;\n  // Marker 的属性发生变化后的回调\n  onChange: onSyncFunc = () =\u003e {};\n\n  // 其他属性\n  // ...\n\n  public static createMarker = (page?: WhitePage): BaseMarker =\u003e {\n    const marker = new BaseMarker();\n    marker.page = page;\n    marker.init();\n    return marker;\n  };\n\n  // 响应事件变化\n  public reactToManipulation(\n    type: EventType,\n    { dx, dy, pos }: { dx?: number; dy?: number; pos?: PositionType } = {},\n  ) {\n    //  ...\n  }\n\n  /** 响应元素视图状态变化 */\n  public manipulate = (ev: MouseEvent) =\u003e {\n    // ...\n  };\n\n  public endManipulation() {\n    // ...\n  }\n\n  public select() {\n    // ...\n  }\n\n  public deselect() {\n    // ...\n  }\n\n  /** 生成某个快照 */\n  public captureSnap(): MarkerSnap {\n    // ...\n  }\n\n  /** 应用某个快照 */\n  public applySnap(snap: MarkerSnap): void {\n    // ...\n  }\n\n  /** 移除该 Marker */\n  public destroy() {\n    this.visual.style.display = 'none';\n  }\n\n  protected resize(x: number, y: number, cb?: Function) {\n    return;\n  }\n  protected resizeByEvent(x: number, y: number, pos?: PositionType) {\n    return;\n  }\n\n  public move = (dx: number, dy: number) =\u003e {\n    // ...\n  };\n\n  /** Move to relative position */\n  public moveTo = (x: number, y: number) =\u003e {\n    // ...\n  };\n\n  /** Init base marker */\n  protected init() {\n    // ...\n  }\n\n  protected addToVisual = (el: SVGElement) =\u003e {\n    this.visual.appendChild(el);\n  };\n\n  protected addToRenderVisual = (el: SVGElement) =\u003e {\n    this.renderVisual.appendChild(el);\n  };\n\n  protected onMouseDown = (ev: MouseEvent) =\u003e {\n    // ...\n  };\n\n  protected onMouseUp = (ev: MouseEvent) =\u003e {\n    // ...\n  };\n\n  protected onMouseMove = (ev: MouseEvent) =\u003e {\n    // ...\n  };\n}\n```\n\n这里关于 Marker 的内部实现可以参考具体的 Marker，另外值得一提的是，想 LinearMarker, 或者 RectangleMarker 中，其需要响应对关键点拖拽引发的伸缩事件，这里的拖拽点是自定义的 Grip 组件。\n\n## Event System | 事件系统\n\n事件系统，最基础的理解就是用户的任何操作都会触发事件，也可以通过外部传入某个事件的方式来触发白板的界面变化。事件类型分为 Snapshot（snap）与 Key Actions（ka）两种。\n\n首先是 Snapshot 事件，即快照事件；快照会记录完整的状态，整个白板可以从快照中快速恢复。白板级别的快照如下：\n\n```ts\n{\n  id: this.id,\n  sources: this.sources,\n  pageIds: this.pages.map(page =\u003e page.id),\n  visiblePageIndex: this.visiblePageIndex,\n  pages: this.pages.map(p =\u003e p.captureSnap())\n}\n```\n\n如果是 Shallow 模式，则不会下钻到具体的页面的快照。页面的快照即是 Marker 快照构成，每个 Marker 的快照则是朴素对象：\n\n```ts\n{\n  id: this.id,\n  type: this.type,\n  isActive: this.isActive,\n  x: this.x,\n  y: this.y\n}\n```\n\n一般来说，Whiteboard 会定期分发快照，可以通过 snapInterval 来控制间隔。而关键帧事件，则会在每一次界面变动时触发；该事件内建了 Debounce，但仍然会有比较多的数目。因此可以通过 onlyEmitSnap 来控制是否仅使用快照事件来同步。\n\n关键帧事件的定义如下：\n\n```ts\nexport interface SyncEvent {\n  target: TargetType;\n\n  // 当前事件触发者的 ID\n  id?: string;\n  parentId?: string;\n  event: EventType;\n  marker?: MarkerData;\n  border?: WhiteboardSnap;\n  timestamp?: number;\n}\n```\n\n譬如当某个 Marker 发生移动时候，其会触发如下的事件：\n\n```ts\nthis.onChange({\n  target: 'marker',\n  id: this.id,\n  event: 'moveMarker',\n  marker: { dx, dy },\n});\n```\n\n仅在 WhiteBoard 与 WhitePage 级别提供了事件的响应，而在 Drawboard 与 Marker 级别提供了事件的触发。\n\n# Todos\n\n- [x] 结构化事件信息，添加绝对时间戳以适应重放的需求；将 WhitePage 中的事件响应统一提取到 Whiteboard 中。\n- [x] 引入全量的状态订正，每 5 秒订正一次，设置线性 Marker 的全量同步规则\n- [x] 设置矩形类 Marker 的全量同步规则，设置仅全量同步模式\n- [x] 将白板划分为 Whiteboard, MirrorWhiteboard, ReplayWhiteboard 三种模式，开始编写录播模式，修复增量同步与全量同步冲突的问题。\n- [x] 根据获得到的事件的时间进行重播，完善录播模式功能。\n- [x] 优化 Toolbar 样式，增加 Toolbar 拖拽功能\n- [x] 增加拖拽绘制功能\n- [x] 添加全屏的绘制功能，全屏绘制会基于新的全局 div 元素，而非直接将当前元素扩大化\n- [ ] 添加 Whiteboard 的 Loading 界面\n- [ ] 支持编辑中途的缩放能力，将全屏的画板与局部画板的事件达到同步\n\n# About\n\n## Motivation \u0026 Credits\n\n- [markerjs](https://markerjs.com/)\n\n- [WeOutline](https://github.com/ipeychev/weoutline): WeOutline is a shared whiteboard, designed to work among distributed teams\n\n- [screenshots](https://github.com/nashaofu/screenshots): electron 截图插件和 react 截图界面插件\n\n## Copyright \u0026 More | 延伸阅读\n\n![License: CC BY-NC-SA 4.0](https://img.shields.io/badge/License-CC%20BY--NC--SA%204.0-lightgrey.svg) ![](https://parg.co/bDm)\n\n笔者所有文章遵循[知识共享 署名 - 非商业性使用 - 禁止演绎 4.0 国际许可协议](https://creativecommons.org/licenses/by-nc-nd/4.0/deed.zh)，欢迎转载，尊重版权。您还可以前往 [NGTE Books](https://ng-tech.icu/books/) 主页浏览包含知识体系、编程语言、软件工程、模式与架构、Web 与大前端、服务端开发实践与工程架构、分布式基础架构、人工智能与深度学习、产品运营与创业等多类目的书籍列表：\n\n[![NGTE Books](https://s2.ax1x.com/2020/01/18/19uXtI.png)](https://ng-tech.icu/books/)\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fwx-chevalier%2Fweb-whiteboard","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Fwx-chevalier%2Fweb-whiteboard","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Fwx-chevalier%2Fweb-whiteboard/lists"}