This sample demonstrates how to automatically generate thumbnails for each images that are uploaded to Firebase Storage.

See file functions/index.js for the thumbnail generation code.

The thumbnail generation is performed using ImageMagick which is installed by default on all Cloud Functions instances. This is a CLI so we execute the command from node using the child-process-promise package. The image is first downloaded locally from the Firebase Storage bucket to the tmp folder using the google-cloud SDK.

The dependencies are listed in functions/package.json .

The function triggers on upload of any file to your Firebase project's default Cloud Storage bucket.

To deploy and test the sample:

• Create a Firebase project on the Firebase Console and visit the Storage tab.
• Clone this repo: git clone https://github.com/firebase/functions-samples .
• Open this sample's directory: cd functions-samples/generate-thumbnail
• Setup your project by running firebase use --add and select the project you had created.
• Install dependencies in the functions directory: cd functions; npm install; cd -
• Deploy your project using firebase deploy
• Go to your project's Cloud Console > IAM & admin > IAM , Find the App Engine default service account and add the Service Account Token Creator role to that member. This will allow your app to create signed public URLs to the images.
• Go to the Firebase Console Storage tab and upload an image. After a short time an thumbnail image with the same name but a thumb_ prefix will be created in the same folder (make sure you refresh the UI to see the new file).
• Go to the Firebase Console Database (Realtime Database not Cloud Firestore) tab and see that a child of images has been created containing the Signed URLs for both images.