Google Cloud Functions: Strip exif from image files when added to Google Cloud Storage

index.js

const functions = require('@google-cloud/functions-framework');
const { Storage } = require('@google-cloud/storage');
const ExifTransformer = require('exif-be-gone');
const stream = require('stream');
const util = require('util');

const storage = new Storage();

const pipeline = util.promisify(stream.pipeline);

// Register a CloudEvent callback with the Functions Framework that will
// be triggered by Cloud Storage.
functions.cloudEvent('helloGCS', async cloudEvent => {
  console.info(`Event ID: ${cloudEvent.id}`);
  console.info(`Event Type: ${cloudEvent.type}`);

  const file = cloudEvent.data;
  console.info(`Bucket: ${file.bucket}`);
  console.info(`File: ${file.name}`);
  console.info(`Metageneration: ${file.metageneration}`);
  console.info(`Created: ${file.timeCreated}`);
  console.info(`Updated: ${file.updated}`);

  const bucket = storage.bucket(file.bucket);
  const remoteFile = bucket.file(file.name);
  const contentType = file.contentType;

  // Fetch the metadata of the file
  const [metadata] = await remoteFile.getMetadata();
  console.info(`Metadata: ${JSON.stringify(metadata.metadata)}`);

  // Check if metadata contains "strip-exif" 
  if (metadata.metadata && metadata.metadata['strip-exif'] === 'false') {
    console.info('Metadata has strip-exif flag set to false. Skipping exif removal.');
    return;
  }

  // Check if the file has already been processed
  if (metadata.metadata && metadata.metadata.processed) {
    console.info('File has already been processed');
    return;
  }

  // Check if the file is an image
  if (!contentType.startsWith('image/')) {
    console.info('Uploaded file is not an image');
    return;
  }

  remoteFile.download((err, buffer) => {
    if (err) {
      console.error('Error downloading file:', err);
      return;
    }

    const reader = stream.Readable.from(buffer);
    const writer = new stream.PassThrough();

    reader.pipe(new ExifTransformer()).pipe(writer);

    writer.on('data', async modifiedBuffer => {
      await remoteFile.save(modifiedBuffer);

      // Update the metadata of the file
      await remoteFile.setMetadata({
        metadata: {
          processed: 'true',
          'processed-by': 'functions/us-central1/strip-exif'
        }
      });

      console.info('EXIF data stripped and image saved back to bucket');
    });

    writer.on('error', error => {
      console.error('Error processing image:', error);
    });
  });

});

package.json

{
  "dependencies": {
    "@google-cloud/functions-framework": "^3.0.0",
    "@google-cloud/storage": "^7.0.1",
    "exif-be-gone": "^1.3.2"
  }
}