generate thumnail firebase javascript

I created a triggered function on firebase-cloud-function that can auto generate a thumnail for every image uploded on cloud storage. but every upload action i got this error

enter image description here

I coppy/paste the code from firebase github repo and a i follow all the instruction this is the code

    "use strict";

const functions = require("firebase-functions");
const mkdirp = require("mkdirp");
const admin = require("firebase-admin");
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 = 200;
const THUMB_MAX_WIDTH = 200;
// 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.
exports.generateThumbnail =
  .onFinalize(async (object) => {
    console.log("I'm an object hhhhhhhhhhhhhhhhhhhh");
    // File and directory paths.
    const filePath =;
    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/")) {
      return functions.logger.log("This is not an image.");

    // Exit if the image is already a thumbnail.
    if (fileName.startsWith(THUMB_PREFIX)) {
      return functions.logger.log("Already a Thumbnail.");

    // Cloud Storage files.
    const 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.
    await mkdirp(tempLocalDir);
    // Download file from bucket.
    await{ destination: tempLocalFile });
    functions.logger.log("The file has been downloaded to", tempLocalFile);
    // Generate a thumbnail using ImageMagick.
    await spawn(
      { capture: ["stdout", "stderr"] }
    functions.logger.log("Thumbnail created at", tempLocalThumbFile);
    // Uploading the Thumbnail.
    await bucket.upload(tempLocalThumbFile, {
      destination: thumbFilePath,
      metadata: metadata,
    functions.logger.log("Thumbnail uploaded to Storage at", thumbFilePath);
    // Once the image has been uploaded delete the local files to free up disk space.
    // Get the Signed URLs for the thumbnail and original image.
    /* const results = await Promise.all([
        action: "read",
        expires: "03-01-2500",
        action: "read",
        expires: "03-01-2500",
    functions.logger.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
    /*await admin
      .push({ path: fileUrl, thumbnail: thumbFileUrl });*/
    return; // functions.logger.log("Thumbnail URLs saved to database.");
  • This is my IAM configuration enter image description here


As the error suggests, you need to add IAM role that includes storage.object access. You can start with Storage Admin role. If it’s working, you can start experimenting with more specific roles (eg. Storage Object Creator + Viewer)