Potter's Blog

Appearance

Return to top
On this page

Electron 入门实战 03：实现一个截图功能

实现效果

实现思路

  1. 创建两个window，一个叫mainWindow，一个叫cutWindow
  2. mainWindow：主界面用来展示截图结果
  3. cutWindow：截图窗口，加载截图页面和截图交互逻辑
  4. mainWindow 页面点击截图，让cutWIndow 来实现具体截图逻辑
  5. cutWindow：截图完后把截图send给mainWindow页面

截图过程-时序图

创建项目

我在网上找了一大圈，没有找到一个合适的模板，要么环境太老、要么配置各种缺失不完善、要么打包出来各种问题等等，说实话坑还真不少，无意间找到一个特别好的脚手架，它简单又完善。推荐给大家：electron-vite ，所以接下来直接用创建命令

jsx
yarn create @quick-start/electron

安装依赖

  • vue-router：切换加载首页和截图页面
  • konva：完成截图交互的库
jsx
yarn add konva vue-router

核心代码

为了更好的展示添加的内容，提供如下目录结构图方便理解

目录结构

主进程

  • src/main/index.js

    jsx
    import {
  app,
  shell,
  BrowserWindow,
  ipcMain,
  screen,
  desktopCapturer,
  globalShortcut
} from 'electron'
import { join } from 'path'
import { electronApp, optimizer, is } from '@electron-toolkit/utils'
import icon from '../../resources/icon.png?asset'

let mainWindow
let cutWindow

function closeCutWindow() {
  cutWindow && cutWindow.close()
  cutWindow = null
}

function createMainWindow() {
  mainWindow = new BrowserWindow({
    width: 900,
    height: 670,
    show: false,
    autoHideMenuBar: true,
    ...(process.platform === 'linux' ? { icon } : {}),
    webPreferences: {
      preload: join(__dirname, '../preload/index.js'),
      sandbox: false
    }
  })

  mainWindow.on('ready-to-show', () => {
    mainWindow.show()
  })

  mainWindow.webContents.setWindowOpenHandler((details) => {
    shell.openExternal(details.url)
    return { action: 'deny' }
  })

  console.log('loadURL:', process.env['ELECTRON_RENDERER_URL'])

  if (is.dev && process.env['ELECTRON_RENDERER_URL']) {
    mainWindow.loadURL(process.env['ELECTRON_RENDERER_URL'])
  } else {
    mainWindow.loadFile(join(__dirname, '../renderer/index.html'))
  }

  mainWindow.on('closed', () => {
    closeCutWindow()
  })
}

function registerShortcut() {
  //! 截图快捷键
  globalShortcut.register('CommandOrControl+Alt+C', () => {
    openCutScreen()
  })
  globalShortcut.register('Esc', () => {
    closeCutWindow()
    mainWindow.show()
  })
  globalShortcut.register('Enter', sendFinishCut)
}

app.whenReady().then(() => {
  // Set app user model id for windows
  electronApp.setAppUserModelId('com.electron')

  // Default open or close DevTools by F12 in development
  // and ignore CommandOrControl + R in production.
  // see https://github.com/alex8088/electron-toolkit/tree/master/packages/utils
  //! 开发模式：win 环境F12 和 mac os 环境：CommandOrControl + R 打开 DevTools
  app.on('browser-window-created', (_, window) => {
    optimizer.watchWindowShortcuts(window)
  })

  createMainWindow()
  registerShortcut()
  openMainListener()

  app.on('activate', function () {
    if (BrowserWindow.getAllWindows().length === 0) createMainWindow()
  })
})

app.on('window-all-closed', () => {
  if (process.platform !== 'darwin') {
    globalShortcut.unregisterAll()
    app.quit()
  }
})

function getSize() {
  const { size, scaleFactor } = screen.getPrimaryDisplay()
  return {
    width: size.width * scaleFactor,
    height: size.height * scaleFactor
  }
}

function createCutWindow() {
  const { width, height } = getSize()
  cutWindow = new BrowserWindow({
    width,
    height,
    autoHideMenuBar: true,
    useContentSize: true,
    movable: false,
    frame: false,
    resizable: false,
    hasShadow: false,
    transparent: true,
    fullscreenable: true,
    fullscreen: true,
    simpleFullscreen: true,
    alwaysOnTop: false,
    webPreferences: {
      preload: join(__dirname, '../preload/index.js'),
      nodeIntegration: true,
      contextIsolation: false
    }
  })

  console.log('createCutWindow:', is.dev, process.env['ELECTRON_RENDERER_URL'])

  if (is.dev && process.env['ELECTRON_RENDERER_URL']) {
    let url = process.env['ELECTRON_RENDERER_URL'] + '/#/cut'
    console.log('createCutWindow: loadURL=', url)
    cutWindow.loadURL(url)
  } else {
    cutWindow.loadFile(path.join(__dirname, '../renderer/index.html'))
  }

  cutWindow.maximize()
  cutWindow.setFullScreen(true)
}

function sendFinishCut() {
  cutWindow && cutWindow.webContents.send('FINISH_CUT')
}

function openCutScreen() {
  closeCutWindow()
  mainWindow.hide()
  createCutWindow()
  cutWindow.show()
}

function openMainListener() {
  ipcMain.on('OPEN_CUT_SCREEN', openCutScreen)
  ipcMain.on('SHOW_CUT_SCREEN', async (e) => {
    let sources = await desktopCapturer.getSources({
      types: ['screen'],
      thumbnailSize: getSize()
    })
    cutWindow && cutWindow.webContents.send('GET_SCREEN_IMAGE', sources[0])
  })
  ipcMain.on('FINISH_CUT_SCREEN', async (e, cutInfo) => {
    closeCutWindow()
    mainWindow.webContents.send('GET_CUT_INFO', cutInfo)
    mainWindow.show()
  })
  ipcMain.on('CLOSE_CUT_SCREEN', async (e) => {
    closeCutWindow()
    mainWindow.show()
  })
}

渲染器

  • scr/main.js

    jsx
    import { createApp } from 'vue'
import App from './App.vue'
import router from './router'

const app = createApp(App)
app.use(router)
app.mount('#app')

  • src/router/index.js

    jsx
    import { createRouter, createWebHashHistory } from 'vue-router'

const routes = [
  { path: '/', redirect: '/home' },
  {
    path: '/home',
    name: 'home',
    component: () => import('../pages/Home/index.vue')
  },
  {
    path: '/cut',
    name: 'cut',
    component: () => import('../pages/Cut/index.vue')
  }
]

const router = createRouter({
  history: createWebHashHistory(),
  routes
})

export default router

  • src/App.vue

    jsx
    <template>
  <router-view>
  </router-view>
</template>

<script setup>
</script>

<style lang="less">
@import './assets/css/styles.less';
</style>

  • src/pages/index.vue：首页

    jsx
    <template>
	<div class="container">
		<button @click="handleCutScreen">截屏</button>
		<div>
			<img :src="previewImage"
					 style="max-width: 100%" />
		</div>
	</div>
</template>

<script setup>
import { ref } from "vue";
const { ipcRenderer } = window.electron;
const previewImage = ref("");

async function handleCutScreen() {
	await ipcRenderer.send("OPEN_CUT_SCREEN");
	ipcRenderer.removeListener("GET_CUT_INFO", getCutInfo);
	ipcRenderer.on("GET_CUT_INFO", getCutInfo);
}

function getCutInfo(event, pic) {
	previewImage.value = pic;
}
</script>

  • src/pages/cut.vue：截图界面

    jsx
    <template>
	<div class="container"
			 :style="'background-image:url(' + bg + ')'"
			 ref="container"
			 @mousedown="onMouseDown"
			 @mousemove="onMouseMove"
			 @mouseup="onMouseUp">
	</div>
</template>
<script setup>
import Konva from "konva";
import { ref, onMounted } from "vue";

const { ipcRenderer } = window.electron;
let container = ref(null);
let bg = ref("");
let stage, layer, rect, transformer;

onMounted(() => {
	ipcRenderer.send("SHOW_CUT_SCREEN");
	ipcRenderer.removeListener("GET_SCREEN_IMAGE", getSource);
	ipcRenderer.on("GET_SCREEN_IMAGE", getSource);
	ipcRenderer.on("FINISH_CUT", confirmCut);
});

async function getSource(event, source) {
	const { thumbnail } = source;
	const pngData = await thumbnail.toDataURL("image/png");
	bg.value = pngData;
	render();
}

function render() {
	stage = createStage();
	layer = createLayer(stage);
}

function createStage() {
	return new Konva.Stage({
		container: container.value,
		width: window.innerWidth,
		height: window.innerHeight,
	});
}

function createLayer(stage) {
	let layer = new Konva.Layer();
	stage.add(layer);
	layer.draw();
	return layer;
}

function createRect(layer, x, y, width, height, alpha, draggable) {
	let rect = new Konva.Rect({
		x,
		y,
		width,
		height,
		fill: `rgba(0,0,255,${alpha})`,
		draggable
	});
	layer.add(rect);
	return rect;
}

let isDown = false;
let rectOption = {};
function onMouseDown(e) {
	if (rect || isDown) {
		return;
	}
	isDown = true;
	const { pageX, pageY } = e;
	rectOption.x = pageX || 0;
	rectOption.y = pageY || 0;
	rect = createRect(layer, pageX, pageY, 0, 0, 0.25, false);
	rect.draw();
}

function onMouseMove(e) {
	if (!isDown) return;
	const { pageX, pageY } = e;
	let w = pageX - rectOption.x;
	let h = pageY - rectOption.y;
	rect.remove();
	rect = createRect(layer, rectOption.x, rectOption.y, w, h, 0.25, false);
	rect.draw();
}

function onMouseUp(e) {
	if (!isDown) {
		return;
	}
	isDown = false;
	const { pageX, pageY } = e;
	let w = pageX - rectOption.x;
	let h = pageY - rectOption.y;
	rect.remove();
	rect = createRect(layer, rectOption.x, rectOption.y, w, h, 0, true);
	rect.draw();
	transformer = createTransformer(rect);
	layer.add(transformer);
}

function createTransformer(rect) {
	let transformer = new Konva.Transformer({
		nodes: [rect],
		rotateAnchorOffset: 60,
		enabledAnchors: ['top-left', 'top-right', 'bottom-left', 'bottom-right']
	});
	return transformer
}

/**
 * 根据选择区域生成图片
 * @param {*} info 
 */
async function getCutImage(info) {
	const { x, y, width, height } = info;
	let img = new Image();
	img.src = bg.value;
	let canvas = document.createElement("canvas");
	let ctx = canvas.getContext("2d");
	canvas.width = ctx.width = width;
	canvas.height = ctx.height = height;
	ctx.drawImage(img, -x, -y, window.innerWidth, window.innerHeight);
	return canvas.toDataURL("image/png");
}

/**
 * 确认截图
 */
async function confirmCut() {
	const { width, height, x, y, scaleX = 1, scaleY = 1 } = rect.attrs;
	let _x = width > 0 ? x : x + width * scaleX;
	let _y = height > 0 ? y : y + height * scaleY;
	let pic = await getCutImage({
		x: _x,
		y: _y,
		width: Math.abs(width) * scaleX,
		height: Math.abs(height) * scaleY,
	});
	ipcRenderer.send("FINISH_CUT_SCREEN", pic);
}

/**
 * 关闭截图
 */
function closeCut() {
	ipcRenderer.send("CLOSE_CUT_SCREEN");
}
</script>

<style lang="scss" scoped>
.container {
	position: fixed;
	top: 0;
	bottom: 0;
	left: 0;
	right: 0;
	width: 100%;
	height: 100%;
	overflow: hidden;
	background-color: transparent;
	background-size: 100% 100%;
	background-repeat: no-repeat;
	border: 2px solid blue;
	box-sizing: border-box;
}
</style>

总结

虽然实现了核心功能，但是仅支持主屏幕截图，不支持多屏幕截图，同时还遗留诸多问题，后面单独一篇更新解决

完整demo ：传送门，顺便帮忙点个star，感谢~

参考文献

Released under the MIT License.

Copyright © 2019-present Potter