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Electron Desktop App Development · Leçon

Capture d’écran et médias

Découvrez comment accéder aux fonctionnalités de capture d’écran et aux appareils multimédias, puis les intégrer à vos applications de bureau Electron.

Capture d’écran et médias est une leçon Electron Desktop App Development gratuite sur CoddyKit. Ceci est la leçon 3 sur 4. Tu peux lire la leçon complète ci-dessous gratuitement — puis la pratiquer en direct dans le navigateur avec un éditeur de code intégré et un tuteur IA 24/7. Elle fait partie du parcours d'apprentissage Electron Desktop App Development, et ta progression se synchronise sur le web et l'application CoddyKit. Le cours Electron Desktop App Development comprend 4 leçons au total.

Certaines parties de cette leçon n'ont pas encore été traduites et s'affichent en anglais.

Accessing Camera & Screen

Electron lets your desktop app use native features like cameras, microphones, and even capture the screen. This opens up possibilities for video calls, screen recording, and more!

We'll explore how to list available devices, display live camera feeds, and capture your desktop or specific windows.

Discovering Your Devices

Before using a camera or microphone, you can discover what's available on the user's system. The navigator.mediaDevices.enumerateDevices() method provides a list of all connected media input and output devices.

Run this code to see your devices. You might need to grant permission to access devices.

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

function createWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 450,
    webPreferences: {
      nodeIntegration: true,
      contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
    }
  });

  const htmlContent = `
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <title>Media Devices</title>
    </head>
    <body>
        <h1>Available Media Devices</h1>
        <ul id="device-list"></ul>

        <script>
            async function getMediaDevices() {
                try {
                    const devices = await navigator.mediaDevices.enumerateDevices();
                    const list = document.getElementById('device-list');
                    if (devices.length === 0) {
                        list.innerHTML = '<li>No media devices found or permission denied.</li>';
                        return;
                    }
                    devices.forEach(device => {
                        const li = document.createElement('li');
                        li.textContent = `Kind: ${device.kind}, Label: ${device.label || 'Unknown'}`; 
                        list.appendChild(li);
                    });
                } catch (err) {
                    console.error('Error listing devices:', err);
                    document.getElementById('device-list').innerHTML = `<li>Error: ${err.message}</li>`;
                }
            }
            getMediaDevices();
        </script>
    </body>
    </html>
  `;
  win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
  if (BrowserWindow.getAllWindows().length === 0) createWindow();
});

Displaying Camera Stream

To display a live camera feed, we use navigator.mediaDevices.getUserMedia(). This method requests access to a media input device (like a camera) and, if granted, provides a MediaStream.

This stream can then be displayed in a <video> element. Try running this example:

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

function createWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 450,
    webPreferences: {
      nodeIntegration: true,
      contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
    }
  });

  const htmlContent = `
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <title>Camera Stream</title>
    </head>
    <body>
        <h1>My Camera Feed</h1>
        <video id="camera-feed" autoplay style="width:100%; height:auto;"></video>
        <p id="status"></p>

        <script>
            async function startCamera() {
                const video = document.getElementById('camera-feed');
                const status = document.getElementById('status');
                try {
                    const stream = await navigator.mediaDevices.getUserMedia({
                        video: true // Request video access
                    });
                    video.srcObject = stream;
                    status.textContent = 'Camera feed active.';
                } catch (err) {
                    console.error('Error accessing camera:', err);
                    status.textContent = `Error: ${err.message}. Please grant camera permission.`;
                }
            }
            startCamera();
        </script>
    </body>
    </html>
  `;
  win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
  if (BrowserWindow.getAllWindows().length === 0) createWindow();
});

User Permissions & Errors

Accessing media devices like cameras and microphones requires explicit user permission. When getUserMedia() is called, the operating system will typically prompt the user for consent.

  • Your application should always be ready to handle cases where the user grants or denies permission.
  • Catching errors from getUserMedia() (e.g., NotAllowedError) helps you inform the user about permission issues.

Understanding DesktopCapturer

Electron provides the desktopCapturer module, a powerful tool that allows your app to capture video and audio from the entire screen, specific windows, or individual displays.

This is essential for building features like screen sharing, screen recording, or even taking screenshots of other applications running on the user's desktop.

Getting Screen Sources

To capture a screen or window, you first need to get a list of available sources. desktopCapturer.getSources() provides these, including their IDs, names, and even thumbnails.

This method is available in the renderer process (but usually exposed via a preload script for security). For simplicity in this lesson, we'll access it directly.

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

function createWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 450,
    webPreferences: {
      nodeIntegration: true, // Required for desktopCapturer
      contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
    }
  });

  const htmlContent = `
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <title>Screen Sources</title>
    </head>
    <body>
        <h1>Available Screen Sources</h1>
        <ul id="source-list"></ul>

        <script>
            const { desktopCapturer } = require('electron'); // Access desktopCapturer

            async function getScreenSources() {
                const list = document.getElementById('source-list');
                try {
                    const sources = await desktopCapturer.getSources({
                        types: ['window', 'screen']
                    });

                    if (sources.length === 0) {
                        list.innerHTML = '<li>No screen or window sources found.</li>';
                        return;
                    }

                    sources.forEach(source => {
                        const li = document.createElement('li');
                        li.textContent = `ID: ${source.id}, Name: ${source.name}`; 
                        if (source.thumbnail) {
                            const img = document.createElement('img');
                            img.src = source.thumbnail.toDataURL();
                            img.style.maxWidth = '100px';
                            img.style.marginLeft = '10px';
                            li.appendChild(img);
                        }
                        list.appendChild(li);
                    });
                } catch (err) {
                    console.error('Error getting sources:', err);
                    list.innerHTML = `<li>Error: ${err.message}</li>`;
                }
            }
            getScreenSources();
        </script>
    </body>
    </html>
  `;
  win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
  if (BrowserWindow.getAllWindows().length === 0) createWindow();
});

Displaying a Screen Stream

Once you have a source ID (e.g., from a specific display or window), you can use navigator.mediaDevices.getUserMedia() again. This time, you pass a chromeMediaSource constraint with the desktopCapturer source ID.

This will capture the chosen screen/window and display it in a <video> element, similar to a camera feed.

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

function createWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 450,
    webPreferences: {
      nodeIntegration: true, // Required for desktopCapturer
      contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
    }
  });

  const htmlContent = `
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <title>Screen Capture</title>
    </head>
    <body>
        <h1>Screen Capture Demo</h1>
        <button id="start-capture">Start Screen Capture</button>
        <video id="screen-feed" autoplay style="width:100%; height:auto;"></video>
        <p id="status"></p>

        <script>
            const { desktopCapturer } = require('electron');

            document.getElementById('start-capture').addEventListener('click', async () => {
                const video = document.getElementById('screen-feed');
                const status = document.getElementById('status');
                status.textContent = 'Searching for sources...';

                try {
                    const sources = await desktopCapturer.getSources({
                        types: ['screen'], // Only screens for simplicity
                        thumbnailSize: { width: 1, height: 1 } // No large thumbnails needed
                    });

                    if (sources.length === 0) {
                        status.textContent = 'No screen sources found.';
                        return;
                    }

                    // Take the first screen found
                    const screenSource = sources[0]; 
                    status.textContent = `Capturing: ${screenSource.name}`;

                    const stream = await navigator.mediaDevices.getUserMedia({
                        audio: false, // Can be true for audio
                        video: {
                            mandatory: {
                                chromeMediaSource: 'desktop',
                                chromeMediaSourceId: screenSource.id,
                                minWidth: 1280, minHeight: 720,
                                maxWidth: 1920, maxHeight: 1080
                            }
                        }
                    });
                    video.srcObject = stream;
                    status.textContent = 'Screen capture active.';

                } catch (err) {
                    console.error('Error capturing screen:', err);
                    status.textContent = `Error: ${err.message}.`;
                }
            });
        </script>
    </body>
    </html>
  `;
  win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
  if (BrowserWindow.getAllWindows().length === 0) createWindow();
});

Basic Media Recording

After getting a MediaStream (from a camera or screen), you can record it using the browser's MediaRecorder API. This lets you save the stream as a video or audio file.

The MediaRecorder takes the stream and collects data chunks, which can then be combined into a Blob (e.g., a video file).

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

function createWindow() {
  const win = new BrowserWindow({
    width: 600,
    height: 450,
    webPreferences: {
      nodeIntegration: true,
      contextIsolation: false // Simplifies example for A1. Use preload scripts for security in real apps.
    }
  });

  const htmlContent = `
    <!DOCTYPE html>
    <html>
    <head>
        <meta charset="UTF-8">
        <title>Media Recorder</title>
    </head>
    <body>
        <h1>Simple Recorder</h1>
        <button id="start-cam">Start Camera</button>
        <button id="start-rec" disabled>Record</button>
        <button id="stop-rec" disabled>Stop</button>
        <video id="live-feed" autoplay muted style="width:100%; height:auto;"></video>
        <a id="download-link" style="display:none;">Download Recording</a>
        <p id="status"></p>

        <script>
            const startCamBtn = document.getElementById('start-cam');
            const startRecBtn = document.getElementById('start-rec');
            const stopRecBtn = document.getElementById('stop-rec');
            const downloadLink = document.getElementById('download-link');
            const liveFeed = document.getElementById('live-feed');
            const status = document.getElementById('status');

            let mediaRecorder;
            let recordedChunks = [];
            let currentStream;

            startCamBtn.addEventListener('click', async () => {
                try {
                    currentStream = await navigator.mediaDevices.getUserMedia({ video: true, audio: true });
                    liveFeed.srcObject = currentStream;
                    startRecBtn.disabled = false;
                    startCamBtn.disabled = true;
                    status.textContent = 'Camera ready. Click Record.';
                } catch (err) {
                    status.textContent = `Error: ${err.message}`;
                    console.error('Error starting camera:', err);
                }
            });

            startRecBtn.addEventListener('click', () => {
                recordedChunks = [];
                mediaRecorder = new MediaRecorder(currentStream);
                mediaRecorder.ondataavailable = event => {
                    if (event.data.size > 0) {
                        recordedChunks.push(event.data);
                    }
                };
                mediaRecorder.onstop = () => {
                    const blob = new Blob(recordedChunks, { type: 'video/webm' });
                    const url = URL.createObjectURL(blob);
                    downloadLink.href = url;
                    downloadLink.download = 'electron-recording.webm';
                    downloadLink.style.display = 'block';
                    status.textContent = 'Recording stopped. Download available.';
                };
                mediaRecorder.start();
                startRecBtn.disabled = true;
                stopRecBtn.disabled = false;
                status.textContent = 'Recording...';
            });

            stopRecBtn.addEventListener('click', () => {
                mediaRecorder.stop();
                startRecBtn.disabled = false;
                stopRecBtn.disabled = true;
            });
        </script>
    </body>
    </html>
  `;
  win.loadURL(`data:text/html;charset=utf-8,${encodeURIComponent(htmlContent)}`);
}

app.whenReady().then(createWindow);
app.on('window-all-closed', () => app.quit());
app.on('activate', () => {
  if (BrowserWindow.getAllWindows().length === 0) createWindow();
});

Security Best Practices

When working with native media, always prioritize security. Granting access to cameras, microphones, or screen capture can be sensitive.

  • Request Permissions Wisely: Only ask for permissions when absolutely necessary for your app's functionality.
  • Inform Users: Clearly explain why your app needs access to these native features.
  • Context Isolation & Preload Scripts: For real-world applications, use contextIsolation: true and expose desktopCapturer securely via a preload script. This prevents malicious scripts in the renderer from accessing Node.js APIs directly.

Quick Check: Native Media

Which of the following statements are true regarding accessing native media and screen capture in Electron?

Recap: Native Media

Great job! In this lesson, we explored how Electron applications can interact with native media features:

  • We learned to use navigator.mediaDevices.enumerateDevices() to list available cameras and microphones.
  • We accessed live camera feeds with navigator.mediaDevices.getUserMedia().
  • We discovered the desktopCapturer module for listing and capturing screen or window content.
  • We briefly touched upon using MediaRecorder to save captured media streams.
  • Finally, we highlighted the importance of user permissions and security best practices when handling sensitive native features.

These tools empower you to build rich, interactive desktop applications with powerful media capabilities!

Questions Fréquemment Posées

La leçon « Capture d’écran et médias » est-elle gratuite ?

Oui — le texte complet de « Capture d’écran et médias » est gratuit à lire ici sur le web. Pour la pratiquer de manière interactive (un éditeur de code intégré et un tuteur IA 24/7) et déverrouiller le reste du cours Electron Desktop App Development, passe à CoddyKit PRO. Le cours Electron Desktop App Development comprend 4 leçons au total.

Qu'est-ce que j'apprendrai dans « Capture d’écran et médias » ?

Découvrez comment accéder aux fonctionnalités de capture d’écran et aux appareils multimédias, puis les intégrer à vos applications de bureau Electron. Tu pratiques Electron Desktop App Development avec du code pratique que tu exécutes directement dans le navigateur, et un tuteur IA 24/7 répond à tes questions au fur et à mesure que tu avances dans la leçon.

Dois-je avoir de l'expérience pour commencer Electron Desktop App Development ?

Aucune expérience préalable n'est requise. Electron Desktop App Development sur CoddyKit est structuré pour les débutants jusqu'aux apprenants avancés, donc tu peux commencer ici ou depuis le début et avancer à ton rythme. Ceci est la leçon 3 sur 4.

Combien de temps prend la leçon « Capture d’écran et médias » ?

La plupart des leçons CoddyKit prennent environ 5–10 minutes. Chacune est courte et interactive, tu progresses régulièrement et tu repiques exactement où tu t'es arrêté sur le web et l'app.

Peux-tu écrire et exécuter du code dans cette leçon Electron Desktop App Development ?

Oui. Chaque leçon Electron Desktop App Development inclut un éditeur de code intégré, tu écris et exécutes du vrai code directement dans ton navigateur et tu reçois des retours IA instantanés — aucune configuration locale requise.

Toutes les leçons de ce cours

  1. Utiliser des modules natifs
  2. Applications de zone de notification et badges
  3. Capture d’écran et médias
  4. Surveillance de l’alimentation et du matériel
← Retour à Electron Desktop App Development