feat(vertexai): add Imagen support

packages/firebase_vertexai/firebase_vertexai/example/ios/Runner/AppDelegate.swift

@@ -1,7 +1,7 @@
 import UIKit
 import Flutter
 
-@UIApplicationMain
+@main
 @objc class AppDelegate: FlutterAppDelegate {
   override func application(
     _ application: UIApplication,

packages/firebase_vertexai/firebase_vertexai/example/lib/main.dart

@@ -22,7 +22,7 @@ import 'pages/function_calling_page.dart';
 import 'pages/image_prompt_page.dart';
 import 'pages/token_count_page.dart';
 import 'pages/schema_page.dart';
-import 'pages/storage_uri_page.dart';
+import 'pages/imagen_page.dart';
 
 // REQUIRED if you want to run on Web
 const FirebaseOptions? options = null;
@@ -79,7 +79,7 @@ class _HomeScreenState extends State<HomeScreen> {
           title: 'Function Calling',
         ), // function calling will initial its own model
         ImagePromptPage(title: 'Image Prompt', model: widget.model),
-        StorageUriPromptPage(title: 'Storage URI Prompt', model: widget.model),
+        ImagenPage(title: 'Imagen Model', model: widget.model),
         SchemaPromptPage(title: 'Schema Prompt', model: widget.model),
       ];
 
@@ -134,11 +134,11 @@ class _HomeScreenState extends State<HomeScreen> {
           ),
           BottomNavigationBarItem(
             icon: Icon(
-              Icons.folder,
+              Icons.image_search,
               color: Theme.of(context).colorScheme.primary,
             ),
-            label: 'Storage URI Prompt',
-            tooltip: 'Storage URI Prompt',
+            label: 'Imagen Model',
+            tooltip: 'Imagen Model',
           ),
           BottomNavigationBarItem(
             icon: Icon(

packages/firebase_vertexai/firebase_vertexai/example/lib/pages/image_prompt_page.dart

@@ -89,14 +89,28 @@ class _ImagePromptPageState extends State<ImagePromptPage> {
                   const SizedBox.square(
                     dimension: 15,
                   ),
-                  ElevatedButton(
-                    onPressed: !_loading
-                        ? () async {
-                            await _sendImagePrompt(_textController.text);
-                          }
-                        : null,
-                    child: const Text('Send Image Prompt'),
-                  ),
+                  if (!_loading)
+                    IconButton(
+                      onPressed: () async {
+                        await _sendImagePrompt(_textController.text);
+                      },
+                      icon: Icon(
+                        Icons.image,
+                        color: Theme.of(context).colorScheme.primary,
+                      ),
+                    ),
+                  if (!_loading)
+                    IconButton(
+                      onPressed: () async {
+                        await _sendStorageUriPrompt(_textController.text);
+                      },
+                      icon: Icon(
+                        Icons.storage,
+                        color: Theme.of(context).colorScheme.primary,
+                      ),
+                    )
+                  else
+                    const CircularProgressIndicator(),
                 ],
               ),
             ),
@@ -162,6 +176,49 @@ class _ImagePromptPageState extends State<ImagePromptPage> {
     }
   }
 
+  Future<void> _sendStorageUriPrompt(String message) async {
+    setState(() {
+      _loading = true;
+    });
+    try {
+      final content = [
+        Content.multi([
+          TextPart(message),
+          FileData(
+            'image/jpeg',
+            'gs://vertex-ai-example-ef5a2.appspot.com/foodpic.jpg',
+          ),
+        ]),
+      ];
+      _generatedContent.add(MessageData(text: message, fromUser: true));
+
+      var response = await widget.model.generateContent(content);
+      var text = response.text;
+      _generatedContent.add(MessageData(text: text, fromUser: false));
+
+      if (text == null) {
+        _showError('No response from API.');
+        return;
+      } else {
+        setState(() {
+          _loading = false;
+          _scrollDown();
+        });
+      }
+    } catch (e) {
+      _showError(e.toString());
+      setState(() {
+        _loading = false;
+      });
+    } finally {
+      _textController.clear();
+      setState(() {
+        _loading = false;
+      });
+      _textFieldFocus.requestFocus();
+    }
+  }
+
   void _showError(String message) {
     showDialog<void>(
       context: context,

packages/firebase_vertexai/firebase_vertexai/example/lib/pages/imagen_page.dart

@@ -0,0 +1,229 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:flutter/material.dart';
+import 'package:firebase_vertexai/firebase_vertexai.dart';
+//import 'package:firebase_storage/firebase_storage.dart';
+import '../widgets/message_widget.dart';
+
+class ImagenPage extends StatefulWidget {
+  const ImagenPage({
+    super.key,
+    required this.title,
+    required this.model,
+  });
+
+  final String title;
+  final GenerativeModel model;
+
+  @override
+  State<ImagenPage> createState() => _ImagenPageState();
+}
+
+class _ImagenPageState extends State<ImagenPage> {
+  final ScrollController _scrollController = ScrollController();
+  final TextEditingController _textController = TextEditingController();
+  final FocusNode _textFieldFocus = FocusNode();
+  final List<MessageData> _generatedContent = <MessageData>[];
+  bool _loading = false;
+  late final ImagenModel _imagenModel;
+
+  @override
+  void initState() {
+    super.initState();
+    var generationConfig = ImagenGenerationConfig(
+      negativePrompt: 'frog',
+      numberOfImages: 1,
+      aspectRatio: ImagenAspectRatio.square1x1,
+      imageFormat: ImagenFormat.jpeg(compressionQuality: 75),
+    );
+    _imagenModel = FirebaseVertexAI.instance.imagenModel(
+      model: 'imagen-3.0-generate-001',
+      generationConfig: generationConfig,
+      safetySettings: ImagenSafetySettings(
+        ImagenSafetyFilterLevel.blockLowAndAbove,
+        ImagenPersonFilterLevel.allowAdult,
+      ),
+    );
+  }
+
+  void _scrollDown() {
+    WidgetsBinding.instance.addPostFrameCallback(
+      (_) => _scrollController.animateTo(
+        _scrollController.position.maxScrollExtent,
+        duration: const Duration(
+          milliseconds: 750,
+        ),
+        curve: Curves.easeOutCirc,
+      ),
+    );
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(widget.title),
+      ),
+      body: Padding(
+        padding: const EdgeInsets.all(8),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            Expanded(
+              child: ListView.builder(
+                controller: _scrollController,
+                itemBuilder: (context, idx) {
+                  return MessageWidget(
+                    text: _generatedContent[idx].text,
+                    image: _generatedContent[idx].image,
+                    isFromUser: _generatedContent[idx].fromUser ?? false,
+                  );
+                },
+                itemCount: _generatedContent.length,
+              ),
+            ),
+            Padding(
+              padding: const EdgeInsets.symmetric(
+                vertical: 25,
+                horizontal: 15,
+              ),
+              child: Row(
+                children: [
+                  Expanded(
+                    child: TextField(
+                      autofocus: true,
+                      focusNode: _textFieldFocus,
+                      controller: _textController,
+                    ),
+                  ),
+                  const SizedBox.square(
+                    dimension: 15,
+                  ),
+                  if (!_loading)
+                    IconButton(
+                      onPressed: () async {
+                        await _testImagen(_textController.text);
+                      },
+                      icon: Icon(
+                        Icons.image_search,
+                        color: Theme.of(context).colorScheme.primary,
+                      ),
+                      tooltip: 'Imagen raw data',
+                    )
+                  else
+                    const CircularProgressIndicator(),
+                  // NOTE: Keep this API private until future release.
+                  // if (!_loading)
+                  //   IconButton(
+                  //     onPressed: () async {
+                  //       await _testImagenGCS(_textController.text);
+                  //     },
+                  //     icon: Icon(
+                  //       Icons.imagesearch_roller,
+                  //       color: Theme.of(context).colorScheme.primary,
+                  //     ),
+                  //     tooltip: 'Imagen GCS',
+                  //   )
+                  // else
+                  //   const CircularProgressIndicator(),
+                ],
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<void> _testImagen(String prompt) async {
+    setState(() {
+      _loading = true;
+    });
+
+    var response = await _imagenModel.generateImages(prompt);
+
+    if (response.images.isNotEmpty) {
+      var imagenImage = response.images[0];
+      // Process the image
+      _generatedContent.add(
+        MessageData(
+          image: Image.memory(imagenImage.bytesBase64Encoded),
+          text: prompt,
+          fromUser: false,
+        ),
+      );
+    } else {
+      // Handle the case where no images were generated
+      _showError('Error: No images were generated.');
+    }
+    setState(() {
+      _loading = false;
+      _scrollDown();
+    });
+  }
+  // NOTE: Keep this API private until future release.
+  // Future<void> _testImagenGCS(String prompt) async {
+  //   setState(() {
+  //     _loading = true;
+  //   });
+  //   var gcsUrl = 'gs://vertex-ai-example-ef5a2.appspot.com/imagen';
+
+  //   var response = await _imagenModel.generateImagesGCS(prompt, gcsUrl);
+
+  //   if (response.images.isNotEmpty) {
+  //     var imagenImage = response.images[0];
+  //     final returnImageUri = imagenImage.gcsUri;
+  //     final reference = FirebaseStorage.instance.refFromURL(returnImageUri);
+  //     final downloadUrl = await reference.getDownloadURL();
+  //     // Process the image
+  //     _generatedContent.add(
+  //       MessageData(
+  //         image: Image(image: NetworkImage(downloadUrl)),
+  //         text: prompt,
+  //         fromUser: false,
+  //       ),
+  //     );
+  //   } else {
+  //     // Handle the case where no images were generated
+  //     _showError('Error: No images were generated.');
+  //   }
+  //   setState(() {
+  //     _loading = false;
+  //   });
+  // }
+
+  void _showError(String message) {
+    showDialog<void>(
+      context: context,
+      builder: (context) {
+        return AlertDialog(
+          title: const Text('Something went wrong'),
+          content: SingleChildScrollView(
+            child: SelectableText(message),
+          ),
+          actions: [
+            TextButton(
+              onPressed: () {
+                Navigator.of(context).pop();
+              },
+              child: const Text('OK'),
+            ),
+          ],
+        );
+      },
+    );
+  }
+}