feat(dart): add resize-image quickstart sample by jhuleatt · Pull Request #1272 · firebase/functions-samples

jhuleatt · 2026-04-13T15:03:34Z

Adds a new Dart cloud functions quickstart resize-image which uses firebase_functions to expose an HTTP endpoint imageOptimizer. It dynamically downloads an image from Cloud Storage using the dart_firebase_admin SDK, resizes it using package:image based on width and height query parameters (falling back to a default via defineInt), and saves it back to the Cloud Storage bucket with proper Cache-Control. Subsequent requests to the same image dimensions are served directly from the cache.

PR created automatically by Jules for task 12531933976085189588 started by @jhuleatt

Adds a new Dart cloud functions quickstart `resize-image` which uses `firebase_functions` to expose an HTTP endpoint `imageOptimizer`. It dynamically downloads an image from Cloud Storage using the `dart_firebase_admin` SDK, resizes it using `package:image` based on `width` and `height` query parameters (falling back to a default via `defineInt`), and saves it back to the Cloud Storage bucket with proper `Cache-Control`. Subsequent requests to the same image dimensions are served directly from the cache. Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

google-labs-jules · 2026-04-13T15:03:36Z

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gemini-code-assist

Code Review

This pull request introduces a Dart-based Firebase Cloud Function for image resizing, handling image retrieval, processing, and caching. Key feedback includes correcting the storage path extraction by skipping the function name segment, ensuring download tokens are set in metadata during upload for compatibility, and fixing invalid version constraints in pubspec.yaml. Additionally, redundant metadata checks and unused dependency overrides should be removed to optimize performance and maintainability.

gemini-code-assist · 2026-04-13T15:05:27Z

Dart/quickstarts/resize-image/bin/server.dart

+      final pathSegments = request.url.pathSegments;
+      if (pathSegments.isEmpty || pathSegments.last.isEmpty) {
+        return Response(
+          400,
+          body: 'Missing storage object ID in the request path.',
+        );
+      }
+      final storageObjectId = pathSegments.join('/');


The current logic for extracting the storageObjectId includes the function name (the first path segment) in the object path. In Cloud Functions, the URL path typically starts with the function name (e.g., /imageOptimizer/path/to/image.jpg). Joining all segments will result in imageOptimizer/path/to/image.jpg, which is likely not the intended path in your Storage bucket. You should skip the first segment.

Suggested change

final pathSegments = request.url.pathSegments;

if (pathSegments.isEmpty || pathSegments.last.isEmpty) {

return Response(

400,

body: 'Missing storage object ID in the request path.',

);

}

final storageObjectId = pathSegments.join('/');

final pathSegments = request.url.pathSegments;

if (pathSegments.length < 2 || pathSegments.last.isEmpty) {

return Response(

400,

body: 'Missing storage object ID in the request path.',

);

}

final storageObjectId = pathSegments.skip(1).join('/');

gemini-code-assist · 2026-04-13T15:05:28Z

Dart/quickstarts/resize-image/bin/server.dart

+      await bucket.storage.uploadObject(
+        bucket.name,
+        cachedFileName,
+        encodedBytes,
+        metadata: ObjectMetadata(cacheControl: 'public, max-age=86400'),
+      );


The getDownloadURL method in the Firebase Admin SDK requires a specific metadata field, firebaseStorageDownloadTokens, to be present on the object. Without setting this token during upload, subsequent calls to getDownloadURL will fail. You should generate a unique token and include it in the object's metadata.

Suggested change

await bucket.storage.uploadObject(

bucket.name,

cachedFileName,

encodedBytes,

metadata: ObjectMetadata(cacheControl: 'public, max-age=86400'),

);

// Upload resized image

final downloadToken = DateTime.now().microsecondsSinceEpoch.toString();

await bucket.storage.uploadObject(

bucket.name,

cachedFileName,

encodedBytes,

metadata: ObjectMetadata(

cacheControl: 'public, max-age=86400',

metadata: {'firebaseStorageDownloadTokens': downloadToken},

),

);

gemini-code-assist · 2026-04-13T15:05:28Z

Dart/quickstarts/resize-image/pubspec.yaml

+  sdk: ^3.11.0
+
+dependencies:
+  dart_firebase_admin: ^0.5.0
+  firebase_functions:
+    git:
+      url: https://github.com/firebase/firebase-functions-dart
+      ref: main
+  google_cloud_storage: ^0.6.0
+  image: ^4.8.0
+  path: ^1.9.1
+
+dev_dependencies:
+  build_runner: ^2.10.5
+  lints: ^6.0.0


Several version constraints in the pubspec.yaml appear to be invalid or refer to non-existent future versions. For example, Dart SDK ^3.11.0, image: ^4.8.0, and lints: ^6.0.0 do not exist yet. Please use realistic version constraints based on current stable releases.

environment: sdk: ^3.5.0 dependencies: dart_firebase_admin: ^0.4.0 firebase_functions: git: url: https://github.com/firebase/firebase-functions-dart ref: main google_cloud_storage: ^0.6.0 image: ^4.3.0 path: ^1.9.0 dev_dependencies: build_runner: ^2.4.0 lints: ^4.0.0

gemini-code-assist · 2026-04-13T15:05:28Z

Dart/quickstarts/resize-image/bin/server.dart

+      try {
+        await bucket.storage.objectMetadata(bucket.name, cachedFileName);
+        final downloadUrl = await app.storage().getDownloadURL(
+          bucket,
+          cachedFileName,
+        );
+        return Response.ok(downloadUrl);
+      } on DetailedApiRequestError catch (e) {
+        if (e.status != 404) {
+          rethrow;
+        }
+      }


Calling objectMetadata before getDownloadURL is redundant. The getDownloadURL method internally fetches the object's metadata to retrieve the download token. If the object does not exist, it will throw a 404 error which you are already catching. Removing the explicit metadata check reduces unnecessary API calls.

try { final downloadUrl = await app.storage().getDownloadURL( bucket, cachedFileName, ); return Response.ok(downloadUrl); } on DetailedApiRequestError catch (e) { if (e.status != 404) { rethrow; } }

gemini-code-assist · 2026-04-13T15:05:28Z

Dart/quickstarts/resize-image/pubspec.yaml

+  google_cloud_firestore:
+      git:
+        url: https://github.com/firebase/firebase-admin-dart
+        path: packages/google_cloud_firestore
+        ref: main


The dependency override for google_cloud_firestore is unnecessary as the project does not depend on Firestore. Removing unused overrides keeps the configuration clean.

dart_firebase_admin: git: url: https://github.com/firebase/firebase-admin-dart path: packages/dart_firebase_admin ref: main

jhuleatt · 2026-04-13T18:05:25Z

Dart/quickstarts/resize-image/bin/server.dart

+          bucket,
+          cachedFileName,
+        );
+        return Response.ok(downloadUrl);


now that I think about it, this response (and the one below) should be a permanent redirect to the downloadUrl.

Updated the endpoints to use Response.movedPermanently(downloadUrl) as requested.

jhuleatt · 2026-04-13T18:06:27Z

Dart/quickstarts/resize-image/bin/server.dart

+          : null;
+
+      if (width == null || width <= 0) {
+        return Response(400, body: 'Invalid width parameter.');


Use InvalidArgumentError from https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/error.dart

jhuleatt · 2026-04-13T18:07:38Z

Dart/quickstarts/resize-image/bin/server.dart

+        );
+      } on DetailedApiRequestError catch (e) {
+        if (e.status == 404) {
+          return Response(404, body: 'Original image not found.');


use InvalidArgumentError from https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/error.dart

jhuleatt · 2026-04-13T18:08:42Z

Dart/quickstarts/resize-image/bin/server.dart

+      // Decode image
+      final originalImage = decodeImage(Uint8List.fromList(originalBytes));
+      if (originalImage == null) {
+        return Response(400, body: 'Failed to decode original image.');


This probably means the image isn't actually an image. Use InvalidArgumentError from https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/error.dart

jhuleatt · 2026-04-13T18:09:11Z

Dart/quickstarts/resize-image/bin/server.dart

+      // Encode image
+      final encodedBytes = encodeNamedImage(storageObjectId, resizedImage);
+      if (encodedBytes == null) {
+        return Response(500, body: 'Failed to encode resized image.');


use InternalError https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/error.dart

jhuleatt · 2026-04-13T18:09:28Z

Dart/quickstarts/resize-image/bin/server.dart

+        bucket,
+        cachedFileName,
+      );
+      return Response.ok(downloadUrl);


make this a redirect too

jhuleatt · 2026-04-13T18:10:05Z

Dart/quickstarts/resize-image/bin/server.dart

+          bucket,
+          cachedFileName,
+        );
+        return Response.ok(downloadUrl);


use the logger to log a cache hit or miss https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/logger/logger.dart

Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

The firebase-admin-dart repository recently renamed the primary package from `dart_firebase_admin` to `firebase_admin_sdk`. This updates all the references and overrides in the quickstarts to match the new package name, fixing a CI version solving failure where the `dart_firebase_admin/pubspec.yaml` was not found on the `main` branch. Also updates the overrides' `ref: master` to `ref: main` where applicable since the repository uses `main`. Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

The firebase-admin-dart repository recently renamed the primary package from `dart_firebase_admin` to `firebase_admin_sdk`. This updates all the references and overrides in the quickstarts to match the new package name, fixing a CI version solving failure where the `dart_firebase_admin/pubspec.yaml` was not found on the `main` branch. Also updates the overrides' `ref: master` to `ref: main` where applicable since the repository uses `main`. Also fixes a null type error in parameter parsing. Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

jhuleatt

Use the error classes from https://github.com/firebase/firebase-functions-dart/blob/main/lib/src/https/error.dart for error handling

jhuleatt · 2026-04-13T19:20:06Z

Dart/quickstarts/resize-image/bin/server.dart

+        );
+      } on DetailedApiRequestError catch (e) {
+        if (e.status == 404) {
+          return Response(404, body: 'Original image not found.');


jhuleatt · 2026-04-13T19:20:12Z

Dart/quickstarts/resize-image/bin/server.dart

+      // Decode image
+      final originalImage = decodeImage(Uint8List.fromList(originalBytes));
+      if (originalImage == null) {
+        return Response(400, body: 'Failed to decode original image.');


jhuleatt · 2026-04-13T19:20:16Z

Dart/quickstarts/resize-image/bin/server.dart

+      // Encode image
+      final encodedBytes = encodeNamedImage(storageObjectId, resizedImage);
+      if (encodedBytes == null) {
+        return Response(500, body: 'Failed to encode resized image.');


The firebase-admin-dart repository recently renamed the primary package from `dart_firebase_admin` to `firebase_admin_sdk`. This updates all the references and overrides in the quickstarts to match the new package name, fixing a CI version solving failure where the `dart_firebase_admin/pubspec.yaml` was not found on the `main` branch. Also updates the overrides' `ref: master` to `ref: main` where applicable since the repository uses `main`. Also fixes a null type error in parameter parsing. Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

Adds a new Dart cloud functions quickstart `resize-image` which uses `firebase_functions` to expose an HTTP endpoint `imageOptimizer`. It dynamically downloads an image from Cloud Storage, resizes it using `package:image` based on `width` and `height` query parameters (falling back to a default via `defineInt`), and saves it back to the Cloud Storage bucket with proper `Cache-Control`. Subsequent requests to the same image dimensions are served directly from the cache. Also updates all dart quickstarts to use `firebase_admin_sdk` since the repository recently renamed the primary package from `dart_firebase_admin` to `firebase_admin_sdk`, and points overrides to the `main` branch. Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

…31933976085189588

gemini-code-assist bot reviewed Apr 13, 2026

View reviewed changes

jhuleatt commented Apr 13, 2026

View reviewed changes

google-labs-jules bot and others added 4 commits April 13, 2026 18:10

fix(dart): use movedPermanently redirect for resized image downloads

cbb439b

Co-authored-by: jhuleatt <3759507+jhuleatt@users.noreply.github.com>

jhuleatt commented Apr 13, 2026

View reviewed changes

google-labs-jules bot and others added 4 commits April 13, 2026 19:29

Merge branch 'dart-launch' into feat/dart-resize-image-quickstart-125…

1d18d7e

…31933976085189588

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