electron/docs/fiddles/features/offscreen-rendering/main.js

const { app, BrowserWindow } = require('electron')
const fs = require('fs')
const path = require('path')

app.disableHardwareAcceleration()

let win

app.whenReady().then(() => {
  win = new BrowserWindow({ webPreferences: { offscreen: true } })
  win.loadURL('https://github.com')
  win.webContents.on('paint', (event, dirty, image) => {
    fs.writeFileSync('ex.png', image.toPNG())
  })
  win.webContents.setFrameRate(60)
  console.log(`The screenshot has been successfully saved to ${path.join(process.cwd(), 'ex.png')}`)
})

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

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