firebase functions thumbnail

generateThumb.js

const mkdirp = require('mkdirp-promise');
const gcs = require('@google-cloud/storage')({ keyFilename: 'service-account-key.json' });
const admin = require('firebase-admin');
var serviceAccount = require('./service-account-key.json');

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: 'https://<PROJECT_ID>.firebaseio.com'
});

const spawn = require('child-process-promise').spawn;
const path = require('path');
const os = require('os');
const fs = require('fs');

// Max height and width of the thumbnail in pixels.
const THUMB_MAX_HEIGHT = 640;
const THUMB_MAX_WIDTH = 640;
// Thumbnail prefix added to file names.
const THUMB_PREFIX = 'thumb_';
/**
 * When an image is uploaded in the Storage bucket We generate a thumbnail automatically using
 * ImageMagick.
 * After the thumbnail has been generated and uploaded to Cloud Storage,
 * we write the public URL to the Firebase Realtime Database.
 */
module.exports = (object) => {
    
    const getUIDFromName = (name) => {
        const str = name; // "users/u1xuI9dazWY3U2Ru6ljJEG3v2AD3/90342bac-5028-461d-8bc2-eb2e6b9592f7";
        const regex = /users\/\s*(.*?)\s*\//g;
        const match = regex.exec(str);

        return match[1];
    };

    // File and directory paths.
    const filePath = object.name;
    const UID = getUIDFromName(filePath);
    console.log("generateThumbnail UID", UID);
    const contentType = object.contentType; // This is the image MIME type
    const fileDir = path.dirname(filePath);
    const fileName = path.basename(filePath);
    const thumbFilePath = path.normalize(path.join(fileDir, `${THUMB_PREFIX}${fileName}`));
    const tempLocalFile = path.join(os.tmpdir(), filePath);
    const tempLocalDir = path.dirname(tempLocalFile);
    const tempLocalThumbFile = path.join(os.tmpdir(), thumbFilePath);

    // Exit if this is triggered on a file that is not an image.
    if (!contentType.startsWith('image/')) {
        console.log('This is not an image.');
        return null;
    }

    // Exit if the image is already a thumbnail.
    if (fileName.startsWith(THUMB_PREFIX)) {
        console.log('Already a Thumbnail.');
        return null;
    }

    // Cloud Storage files.
    const bucket = gcs.bucket(object.bucket);
    const file = bucket.file(filePath);
    const thumbFile = bucket.file(thumbFilePath);
    const metadata = {
        contentType: contentType,
        // To enable Client-side caching you can set the Cache-Control headers here. Uncomment below.
        // 'Cache-Control': 'public,max-age=3600',
    };

    // Create the temp directory where the storage file will be downloaded.
    return mkdirp(tempLocalDir).then(() => {
        // Download file from bucket.
        return file.download({ destination: tempLocalFile });
    }).then(() => {
        console.log('The file has been downloaded to', tempLocalFile);
        // Generate a thumbnail using ImageMagick.
        return spawn('convert', [tempLocalFile, '-thumbnail', `${THUMB_MAX_WIDTH}x${THUMB_MAX_HEIGHT}>`, tempLocalThumbFile], { capture: ['stdout', 'stderr'] });
    }).then(() => {
        console.log('Thumbnail created at', tempLocalThumbFile);
        // Uploading the Thumbnail.
        return bucket.upload(tempLocalThumbFile, { destination: thumbFilePath, metadata: metadata });
    }).then(() => {
        console.log('Thumbnail uploaded to Storage at', thumbFilePath);
        // Once the image has been uploaded delete the local files to free up disk space.
        fs.unlinkSync(tempLocalFile);
        fs.unlinkSync(tempLocalThumbFile);
        // Get the Signed URLs for the thumbnail and original image.
        const config = {
            action: 'read',
            expires: '03-01-2500',
        };
        return Promise.all([
            thumbFile.getSignedUrl(config),
            file.getSignedUrl(config),
        ]);
    }).then((results) => {
        console.log('Got Signed URLs.');
        const thumbResult = results[0];
        const originalResult = results[1];
        const thumbFileUrl = thumbResult[0];
        const fileUrl = originalResult[0];
        // Add the URLs to the Database
        return admin.database().ref('users/'+ UID).set({ photo: fileUrl, thumbnail: thumbFileUrl });
    }).then(() => console.log('Thumbnail URLs saved to database.'));
};

index.js

const functions = require('firebase-functions');
const generateThumbnail = require('./generateThumb');

exports.generateThumbnail = functions.storage.object().onFinalize(generateThumbnail);