mirror of https://github.com/electron/electron
87 lines
2.6 KiB
Markdown
87 lines
2.6 KiB
Markdown
# Offscreen Rendering
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## Overview
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Offscreen rendering lets you obtain the content of a `BrowserWindow` in a
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bitmap, so it can be rendered anywhere, for example, on texture in a 3D scene.
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The offscreen rendering in Electron uses a similar approach to that of the
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[Chromium Embedded Framework](https://bitbucket.org/chromiumembedded/cef)
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project.
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_Notes_:
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* There are two rendering modes that can be used (see the section below) and only
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the dirty area is passed to the `paint` event to be more efficient.
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* You can stop/continue the rendering as well as set the frame rate.
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* The maximum frame rate is 240 because greater values bring only performance
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losses with no benefits.
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* When nothing is happening on a webpage, no frames are generated.
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* An offscreen window is always created as a
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[Frameless Window](../tutorial/window-customization.md)..
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### Rendering Modes
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#### GPU accelerated
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GPU accelerated rendering means that the GPU is used for composition. Because of
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that, the frame has to be copied from the GPU which requires more resources,
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thus this mode is slower than the Software output device. The benefit of this
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mode is that WebGL and 3D CSS animations are supported.
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#### Software output device
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This mode uses a software output device for rendering in the CPU, so the frame
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generation is much faster. As a result, this mode is preferred over the GPU
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accelerated one.
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To enable this mode, GPU acceleration has to be disabled by calling the
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[`app.disableHardwareAcceleration()`][disablehardwareacceleration] API.
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## Example
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```fiddle docs/fiddles/features/offscreen-rendering
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const { app, BrowserWindow } = require('electron/main')
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const fs = require('node:fs')
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const path = require('node:path')
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app.disableHardwareAcceleration()
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function createWindow () {
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const win = new BrowserWindow({
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width: 800,
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height: 600,
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webPreferences: {
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offscreen: true
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}
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})
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win.loadURL('https://github.com')
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win.webContents.on('paint', (event, dirty, image) => {
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fs.writeFileSync('ex.png', image.toPNG())
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})
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win.webContents.setFrameRate(60)
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console.log(`The screenshot has been successfully saved to ${path.join(process.cwd(), 'ex.png')}`)
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}
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app.whenReady().then(() => {
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createWindow()
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app.on('activate', () => {
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if (BrowserWindow.getAllWindows().length === 0) {
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createWindow()
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}
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})
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})
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app.on('window-all-closed', () => {
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if (process.platform !== 'darwin') {
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app.quit()
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}
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})
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```
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After launching the Electron application, navigate to your application's
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working folder, where you'll find the rendered image.
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[disablehardwareacceleration]: ../api/app.md#appdisablehardwareacceleration
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