從 Imagen 遷移至 Gemini 圖像模型 (「Nano Banana」)

ImagenGemini


所有 Imagen 模型都已淘汰，並將於 2026 年 6 月 24 日停止運作。這項淘汰和關閉作業適用於整個 Google，以及 Gemini Developer API 和 Vertex AI Gemini API。

為避免服務中斷，請在上述日期前，按照本指南說明，將應用程式從使用 Imagen 模型遷移至使用 Gemini 圖片模型 (「Nano Banana」模型)。

如有與這項淘汰和關閉作業相關的緊急問題，請與 Firebase 支援團隊聯絡。

取代 Gemini 圖片模型

請參閱下表，為應用程式選擇替代的 Gemini 圖片模型。

Imagen 個模型 Gemini 圖像模型 (「Nano Banana」)
imagen-4.0-fast-generate-001 gemini-2.5-flash-image (正式發布)
gemini-3.1-flash-image-preview (含思考層級 MINIMAL)
imagen-4.0-generate-001 gemini-2.5-flash-image (GA)
gemini-3.1-flash-image-preview (with thinking level HIGH)
imagen-4.0-ultra-generate-001 gemini-2.5-flash-image (GA)
gemini-3-pro-image-preview
imagen-3.0-capability-001 gemini-2.5-flash-image (GA)
gemini-3.1-flash-image-preview

遷移應用程式

本節提供範例，說明如何從 Imagen 模型遷移至 Gemini Image 模型。

根據文字生成圖片

按一下 Gemini API 供應商，即可在這個頁面查看供應商專屬內容和程式碼。

如要以文字生成圖片，請遷移應用程式：

  • 使用適當的替代 Gemini 圖片模型 (例如 gemini-2.5-flash-image)。

  • 建立 GenerativeModel 執行個體 (而非 ImagenModel 執行個體)。

  • 更新模型設定選項，以支援圖片模型。Gemini

    • 設定時，請將回覆模式設為 IMAGE。
      請注意，Gemini圖片模型可設定為同時傳回圖片和文字。

  • (僅限 Vertex AI Gemini API) 將存取模型的位置更新為 Gemini 圖像模型支援的位置。建議使用 global。

Swift

之前


import FirebaseAILogic

// Initialize the Gemini Developer API backend service
let ai = FirebaseAI.firebaseAI(backend: .googleAI())

// Create an `ImagenModel` instance with a model that supports your use case
let model = ai.imagenModel(modelName: "IMAGEN_MODEL_NAME")

// Provide an image generation prompt
let prompt = "An astronaut riding a horse"

// To generate an image, call `generateImages` with the text prompt
let response = try await model.generateImages(prompt: prompt)

// Handle the generated image
guard let image = response.images.first else {
  fatalError("No image in the response.")
}
let uiImage = UIImage(data: image.data)

之後


import FirebaseAILogic

// Initialize the Gemini Developer API backend service
let ai = FirebaseAI.firebaseAI(backend: .googleAI())

// Create a `GenerativeModel` instance with a Gemini model that supports image output
let model = ai.generativeModel(
  modelName: "GEMINI_IMAGE_MODEL_NAME",
  generationConfig: GenerationConfig(
    responseModalities: [.image],
    imageConfig: ImageConfig(aspectRatio: .landscape4x3)
  )
)

// Provide an image generation prompt
let prompt = "An astronaut riding a horse"

// To generate an image, call `generateContent` with the text prompt
let response = try await model.generateContent(prompt)

// Handle the case where no images were generated
guard let inlineDataPart = response.inlineDataParts.first else {
  fatalError("No image in the response.")
}

// Process the image
guard let uiImage = UIImage(data: inlineDataPart.data) else {
  fatalError("Failed to convert data to UIImage.")
}

Kotlin

之前


// Initialize the Gemini Developer API backend service
val ai = Firebase.ai(backend = GenerativeBackend.googleAI())

// Create an `ImagenModel` instance with an Imagen model that supports your use case
val model = ai.imagenModel("IMAGEN_MODEL_NAME")

// Provide an image generation prompt
val prompt = "An astronaut riding a horse"

// To generate an image, call `generateImages` with the text prompt
val imageResponse = model.generateImages(prompt)

// Handle the generated image
val image = imageResponse.images.first()

val bitmapImage = image.asBitmap()

之後


// Initialize the Gemini Developer API backend service
val ai = Firebase.ai(backend = GenerativeBackend.googleAI())

// Create a `GenerativeModel` instance with a Gemini model that supports image output
val model = ai.generativeModel(
    modelName = "GEMINI_IMAGE_MODEL_NAME",
    generationConfig = generationConfig {
      responseModalities = listOf(ResponseModality.IMAGE),
      imageConfig = imageConfig {
        aspectRatio = AspectRatio.LANDSCAPE_4x3
      }
    }
)

// Provide an image generation prompt
val prompt = "An astronaut riding a horse"

// To generate an image, call `generateContent` with the text prompt
val imageResponse = model.generateContent(prompt)

if (imageResponse.finishReason == FinishReason.NO_IMAGE) {
  // Handle the case where no images were generated
} else {
  // Handle the generated image
  val bitmapImage = imageResponse.candidates.first().content.parts.filterIsInstance().firstOrNull()?.image
}

Java

之前


// Initialize the Gemini Developer API backend service
// Create an `ImagenModel` instance with an Imagen model that supports your use case
ImagenModel imagenModel = FirebaseAI.getInstance(GenerativeBackend.googleAI())
        .imagenModel(
                /* modelName */ "IMAGEN_MODEL_NAME");

ImagenModelFutures model = ImagenModelFutures.from(imagenModel);

// Provide an image generation prompt
String prompt = "An astronaut riding a horse";

// To generate an image, call `generateImages` with the text prompt
Futures.addCallback(model.generateImages(prompt), new FutureCallback<ImagenGenerationResponse>() {
    @Override
    public void onSuccess(ImagenGenerationResponse result) {
        if (result.getImages().isEmpty()) {
            Log.d("TAG", "No images generated");
        }
        Bitmap bitmap = result.getImages().get(0).asBitmap();
        // Use the bitmap to display the image in your UI
    }

    @Override
    public void onFailure(Throwable t) {
        // ...
    }
}, Executors.newSingleThreadExecutor());

之後


// Initialize the Gemini Developer API backend service
// Create a `GenerativeModel` instance with a Gemini model that supports image output
GenerativeModel ai = FirebaseAI.getInstance(GenerativeBackend.googleAI()).generativeModel(
    "GEMINI_IMAGE_MODEL_NAME",
    new GenerationConfig.Builder()
        .setResponseModalities(Arrays.asList(ResponseModality.IMAGE))
        .setImageConfig(new ImageConfig(AspectRatio.LANDSCAPE_4x3, null))
        .build()
);

GenerativeModelFutures model = GenerativeModelFutures.from(ai);

// Provide a text prompt instructing the model to generate an image
Content prompt = new Content.Builder()
        .addText("An astronaut riding a horse")
        .build();

// To generate an image, call `generateContent` with the text input
Executor executor = Executors.newSingleThreadExecutor();
ListenableFuture response = model.generateContent(prompt);
Futures.addCallback(response, new FutureCallback() {
    @Override
    public void onSuccess(GenerateContentResponse result) {
        if (result.finishReason == FinishReason.NO_IMAGE) {
            // handle the case where no images were generated
            return;
        }
        // iterate over all the parts in the first candidate in the result object
        for (Part part : result.getCandidates().get(0).getContent().getParts()) {
            if (part instanceof ImagePart) {
                ImagePart imagePart = (ImagePart) part;
                // The returned image as a bitmap
                Bitmap generatedImageAsBitmap = imagePart.getImage();
                break;
            }
        }
    }

    @Override
    public void onFailure(Throwable t) {
        t.printStackTrace();
    }
}, executor);

Web

之前


import { initializeApp } from "firebase/app";
import { getAI, getGenerativeModel, getImagenModel, GoogleAIBackend } from "firebase/ai";

// TODO(developer) Replace the following with your app's Firebase configuration
const firebaseConfig = {
  // ...
};

// Initialize FirebaseApp
const firebaseApp = initializeApp(firebaseConfig);

// Initialize the Gemini Developer API backend service
const ai = getAI(firebaseApp, { backend: new GoogleAIBackend() });

// Create an `ImagenModel` instance with an Imagen model that supports your use case
const model = getImagenModel(ai, { model: "IMAGEN_MODEL_NAME" });

// Provide an image generation prompt
const prompt = "An astronaut riding a horse.";

// To generate an image, call `generateImages` with the text prompt
const response = await model.generateImages(prompt)

// If fewer images were generated than were requested,
// then `filteredReason` will describe the reason they were filtered out
if (response.filteredReason) {
  console.log(response.filteredReason);
}

if (response.images.length == 0) {
  throw new Error("No images in the response.")
}

const image = response.images[0];

之後


import { initializeApp } from "firebase/app";
import {
  getAI,
  getGenerativeModel,
  GoogleAIBackend,
  ResponseModality,
  ImageConfigAspectRatio,
  FinishReason
} from "firebase/ai";

// TODO(developer) Replace the following with your app's Firebase configuration
const firebaseConfig = {
  // ...
};

// Initialize FirebaseApp
const firebaseApp = initializeApp(firebaseConfig);

// Initialize the Gemini Developer API backend service
const ai = getAI(firebaseApp, { backend: new GoogleAIBackend() });

// Create a `GenerativeModel` instance with a model that supports your use case
const model = getGenerativeModel(ai, {
  model: "GEMINI_IMAGE_MODEL_NAME",
  generationConfig: {
    responseModalities: [ResponseModality.IMAGE],
    imageConfig: {
      aspectRatio: ImageConfigAspectRatio.LANDSCAPE_4x3
    }
  },
});

// Provide an image generation prompt
const prompt = "An astronaut riding a horse.";

// To generate an image, call `generateContent` with the text prompt
const result = await model.generateContent(prompt);

// Handle the generated image
try {
  const response = result.response;
  if (response.candidates?.[0].finishReason == FinishReason.NO_IMAGE) {
    // Handle the case where no images were generated
  }
  const inlineDataParts = response.inlineDataParts();
  if (inlineDataParts?.[0]) {
    const image = inlineDataParts[0].inlineData;
    // Use this mimeType and base64 data to display the image using
    // your preferred tooling
    console.log(image.mimeType, image.data);
  }
} catch (err) {
  console.error('Prompt or candidate was blocked:', err);
}

Dart

之前


import 'package:firebase_ai/firebase_ai.dart';
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';

// Initialize FirebaseApp
await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

// Initialize the Gemini Developer API backend service
final ai = FirebaseAI.googleAI();

// Create an `ImagenModel` instance with an Imagen model that supports your use case
final model = ai.imagenModel(model: 'IMAGEN_MODEL_NAME');

// Provide an image generation prompt
const prompt = 'An astronaut riding a horse.';

// To generate an image, call `generateImages` with the text prompt
final response = await model.generateImages(prompt);

if (response.images.isNotEmpty) {
  final image = response.images[0];
  // Process the image
} else {
  // Handle the case where no images were generated
  print('Error: No images were generated.');
}

之後


import 'package:firebase_ai/firebase_ai.dart';
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';

// Initialize FirebaseApp
await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

// Initialize the Gemini Developer API backend service
final ai = FirebaseAI.googleAI();

// Create a `GenerativeModel` instance with a Gemini model that supports image output
final model = ai.generativeModel(
  model: 'GEMINI_IMAGE_MODEL_NAME',
  generationConfig: GenerationConfig(
    responseModalities: [ResponseModalities.image],
    imageConfig: ImageConfig(aspectRatio: ImageAspectRatio.landscape4x3)
  ),
);

// Provide a text prompt instructing the model to generate an image
final prompt = [Content.text('An astronaut riding a horse.')];

// To generate an image, call `generateContent` with the text prompt
final response = await model.generateContent(prompt);
if (response.inlineDataParts.isNotEmpty) {
  final imageBytes = response.inlineDataParts.first.bytes;
  // Process the image
} else {
  // Handle the case where no images were generated
  print('Error: No images were generated.');
}

Unity

之前


using Firebase.AI;

// Initialize the Gemini Developer API backend service
var ai = FirebaseAI.GetInstance(FirebaseAI.Backend.GoogleAI());

// Create an `ImagenModel` instance with a model that supports your use case
var model = ai.GetImagenModel(modelName: "IMAGEN_MODEL_NAME");

// Provide an image generation prompt
var prompt = "An astronaut riding a horse";

// To generate an image, call `generateImages` with the text prompt
var response = await model.GenerateImagesAsync(prompt: prompt);

// Handle the generated image
if (response.Images.Count == 0) {
  throw new Exception("No image in the response.");
}
var image = response.Images[0].AsTexture2D();

之後


using Firebase;
using Firebase.AI;

// Initialize the Gemini Developer API backend service
var ai = FirebaseAI.GetInstance(FirebaseAI.Backend.GoogleAI());

// Create a `GenerativeModel` instance with a Gemini model that supports image output
var model = ai.GetGenerativeModel(
  modelName: "GEMINI_IMAGE_MODEL_NAME",
  generationConfig: new GenerationConfig(
    responseModalities: new[] { ResponseModality.Image },
    imageConfig: new ImageConfig(aspectRatio: ImageConfig.AspectRatio.Landscape4x3)
  )
);

// Provide an image generation prompt
var prompt = "An astronaut riding a horse";

// To generate an image, call `GenerateContentAsync` with the text prompt
var response = await model.GenerateContentAsync(prompt);

if (response.Candidates.First().FinishReason == FinishReason.NoImage) {
  // Handle the case where no images were generated
}

// Handle the generated image
var imageParts = response.Candidates.First().Content.Parts
                         .OfType<ModelContent.InlineDataPart>()
                         .Where(part => part.MimeType == "image/png");

foreach (var imagePart in imageParts) {
  // Load the Image into a Unity Texture2D object
  UnityEngine.Texture2D texture2D = new(2, 2);
  if (texture2D.LoadImage(imagePart.Data.ToArray())) {
    // Do something with the image
  }
}

替代設定選項

本節說明各種模型設定選項的替代方案，協助控管模型的回覆內容。

安全性設定

您可以使用 ImagenSafetySettings，為 Imagen 模型設定安全選項。不過，如果是 Gemini 圖像模型，則需要遷移至 SafetySetting。

模型設定參數

您可以使用 ImagenGenerationConfig 設定 Imagen 模型。不過，對於 Gemini 圖像模型，您需要遷移至使用 GenerationConfig，並視需要使用巢狀 ImageConfig (這項功能適用於 2026 年 5 月初發布的 SDK 版本)。

在 GenerationConfig 中，將回覆模式設為 IMAGE (如本指南稍早的「後」程式碼範例所示)。請注意，您可以選擇設定 Gemini 圖像模型，同時傳回 IMAGE 和 TEXT。

請參閱下表，瞭解如何將模型設定參數從 Imagen 遷移至 Gemini 圖片模型：

Imagen 個模型 Gemini 圖像模型 (「Nano Banana」)
addWatermark

不支援

Gemini 圖像模型一律會傳回附有 SynthID 浮水印的生成圖像。

aspectRatio

在 ImageConfig 中使用 aspectRatio

如需程式碼範例和支援的值，請參閱「Gemini 圖片模型指南」中的「設定圖片生成」。
imageFormat

不支援

Gemini 圖片模型一律會以 PNG 格式傳回生成的圖片。

negativePrompt

不支援

請注意，負面提示是舊版功能，自 imagen-3.0-generate-002 起即不再支援 (或任何 Imagen 4 模型)。
numberOfImages

不支援

Gemini 圖像模型一律只會傳回一張生成的圖片。
如要解決這個問題，可以透過迴圈執行生成作業，達到相同結果。請注意，候選人數無法做為替代方案。

personGeneration

不支援

根據預設，Gemini圖像模型可生成人物圖像。