Generate text from multimodal prompt

This sample demonstrates how to generate text from a multimodal prompt using the Gemini model. The prompt consists of three images and two text prompts. The model generates a text response that describes the images and the text prompts.

Explore further

For detailed documentation that includes this code sample, see the following:

Code sample

C#

Before trying this sample, follow the C# setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI C# API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.


using Google.Api.Gax.Grpc;
using Google.Cloud.AIPlatform.V1;
using Google.Protobuf;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

public class MultimodalMultiImage
{
    public async Task<string> GenerateContent(
        string projectId = "your-project-id",
        string location = "us-central1",
        string publisher = "google",
        string model = "gemini-1.5-flash-001"
    )
    {
        var predictionServiceClient = new PredictionServiceClientBuilder
        {
            Endpoint = $"{location}-aiplatform.googleapis.com"
        }.Build();

        ByteString colosseum = await ReadImageFileAsync(
            "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark1.png");

        ByteString forbiddenCity = await ReadImageFileAsync(
            "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark2.png");

        ByteString christRedeemer = await ReadImageFileAsync(
            "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark3.png");

        var generateContentRequest = new GenerateContentRequest
        {
            Model = $"projects/{projectId}/locations/{location}/publishers/{publisher}/models/{model}",
            Contents =
            {
                new Content
                {
                    Role = "USER",
                    Parts =
                    {
                        new Part { InlineData = new() { MimeType = "image/png", Data = colosseum }},
                        new Part { Text = "city: Rome, Landmark: the Colosseum" },
                        new Part { InlineData = new() { MimeType = "image/png", Data = forbiddenCity }},
                        new Part { Text = "city: Beijing, Landmark: Forbidden City"},
                        new Part { InlineData = new() { MimeType = "image/png", Data = christRedeemer }}
                    }
                }
            }
        };

        using PredictionServiceClient.StreamGenerateContentStream response = predictionServiceClient.StreamGenerateContent(generateContentRequest);

        StringBuilder fullText = new();

        AsyncResponseStream<GenerateContentResponse> responseStream = response.GetResponseStream();
        await foreach (GenerateContentResponse responseItem in responseStream)
        {
            fullText.Append(responseItem.Candidates[0].Content.Parts[0].Text);
        }
        return fullText.ToString();
    }

    private static async Task<ByteString> ReadImageFileAsync(string url)
    {
        using HttpClient client = new();
        using var response = await client.GetAsync(url);
        byte[] imageBytes = await response.Content.ReadAsByteArrayAsync();
        return ByteString.CopyFrom(imageBytes);
    }
}

Go

Before trying this sample, follow the Go setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Go API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"strings"

	"cloud.google.com/go/vertexai/genai"
)

func main() {
	projectID := os.Getenv("GOOGLE_CLOUD_PROJECT")
	location := "us-central1"
	modelName := "gemini-1.5-flash-001"
	temperature := 0.4

	if projectID == "" {
		log.Fatal("require environment variable GOOGLE_CLOUD_PROJECT")
	}

	// construct this multimodal prompt:
	// [image of colosseum] city: Rome, Landmark: the Colosseum
	// [image of forbidden city]  city: Beijing, Landmark: the Forbidden City
	// [new image]

	// create prompt image parts
	// colosseum
	colosseum, err := partFromImageURL("https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark1.png")
	if err != nil {
		log.Fatalf("unable to read image: %v", err)
	}
	// forbidden city
	forbiddenCity, err := partFromImageURL("https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark2.png")
	if err != nil {
		log.Fatalf("unable to read image: %v", err)
	}
	// new image
	newImage, err := partFromImageURL("https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark3.png")
	if err != nil {
		log.Fatalf("unable to read image: %v", err)
	}

	// create a multimodal (multipart) prompt
	prompt := []genai.Part{
		colosseum,
		genai.Text("city: Rome, Landmark: the Colosseum "),
		forbiddenCity,
		genai.Text("city: Beijing, Landmark: the Forbidden City "),
		newImage,
	}

	// generate the response
	err = generateMultimodalContent(os.Stdout, prompt, projectID, location, modelName, float32(temperature))
	if err != nil {
		log.Fatalf("unable to generate: %v", err)
	}
}

// generateMultimodalContent provide a generated response using multimodal input
func generateMultimodalContent(w io.Writer, parts []genai.Part, projectID, location, modelName string, temperature float32) error {
	ctx := context.Background()

	client, err := genai.NewClient(ctx, projectID, location)
	if err != nil {
		log.Fatal(err)
	}
	defer client.Close()

	model := client.GenerativeModel(modelName)
	model.SetTemperature(temperature)

	res, err := model.GenerateContent(ctx, parts...)
	if err != nil {
		return fmt.Errorf("unable to generate contents: %v", err)
	}

	fmt.Fprintf(w, "generated response: %s\n", res.Candidates[0].Content.Parts[0])

	return nil
}

// partFromImageURL create a multimodal prompt part from an image URL
func partFromImageURL(image string) (genai.Part, error) {
	var img genai.Blob

	imageURL, err := url.Parse(image)
	if err != nil {
		return img, err
	}
	res, err := http.Get(image)
	if err != nil || res.StatusCode != 200 {
		return img, err
	}
	defer res.Body.Close()
	data, err := io.ReadAll(res.Body)
	if err != nil {
		return img, fmt.Errorf("unable to read from http: %v", err)
	}

	position := strings.LastIndex(imageURL.Path, ".")
	if position == -1 {
		return img, fmt.Errorf("couldn't find a period to indicate a file extension")
	}
	ext := imageURL.Path[position+1:]

	img = genai.ImageData(ext, data)
	return img, nil
}

Java

Before trying this sample, follow the Java setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Java API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.vertexai.VertexAI;
import com.google.cloud.vertexai.api.Content;
import com.google.cloud.vertexai.api.GenerateContentResponse;
import com.google.cloud.vertexai.generativeai.ContentMaker;
import com.google.cloud.vertexai.generativeai.GenerativeModel;
import com.google.cloud.vertexai.generativeai.PartMaker;
import com.google.cloud.vertexai.generativeai.ResponseHandler;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class MultimodalMultiImage {

  public static void main(String[] args) throws IOException {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "your-google-cloud-project-id";
    String location = "us-central1";
    String modelName = "gemini-1.5-flash-001";

    multimodalMultiImage(projectId, location, modelName);
  }

  // Generates content from multiple input images.
  public static void multimodalMultiImage(String projectId, String location, String modelName)
      throws IOException {
    // Initialize client that will be used to send requests. This client only needs
    // to be created once, and can be reused for multiple requests.
    try (VertexAI vertexAI = new VertexAI(projectId, location)) {
      GenerativeModel model = new GenerativeModel(modelName, vertexAI);

      Content content = ContentMaker.fromMultiModalData(
          PartMaker.fromMimeTypeAndData("image/png", readImageFile(
              "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark1.png")),
          "city: Rome, Landmark: the Colosseum",
          PartMaker.fromMimeTypeAndData("image/png", readImageFile(
              "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark2.png")),
          "city: Beijing, Landmark: Forbidden City",
          PartMaker.fromMimeTypeAndData("image/png", readImageFile(
              "https://storage.googleapis.com/cloud-samples-data/vertex-ai/llm/prompts/landmark3.png"))
      );

      GenerateContentResponse response = model.generateContent(content);

      String output = ResponseHandler.getText(response);
      System.out.println(output);
    }
  }

  // Reads the image data from the given URL.
  public static byte[] readImageFile(String url) throws IOException {
    URL urlObj = new URL(url);
    HttpURLConnection connection = (HttpURLConnection) urlObj.openConnection();
    connection.setRequestMethod("GET");

    int responseCode = connection.getResponseCode();

    if (responseCode == HttpURLConnection.HTTP_OK) {
      InputStream inputStream = connection.getInputStream();
      ByteArrayOutputStream outputStream = new ByteArrayOutputStream();

      byte[] buffer = new byte[1024];
      int bytesRead;
      while ((bytesRead = inputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, bytesRead);
      }

      return outputStream.toByteArray();
    } else {
      throw new RuntimeException("Error fetching file: " + responseCode);
    }
  }
}

Python

Before trying this sample, follow the Python setup instructions in the Vertex AI quickstart using client libraries. For more information, see the Vertex AI Python API reference documentation.

To authenticate to Vertex AI, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import vertexai

from vertexai.generative_models import GenerativeModel, Part

# TODO(developer): Update and un-comment below line
# project_id = "PROJECT_ID"

vertexai.init(project=project_id, location="us-central1")

# Load images from Cloud Storage URI
image_file1 = Part.from_uri(
    "gs://cloud-samples-data/vertex-ai/llm/prompts/landmark1.png",
    mime_type="image/png",
)
image_file2 = Part.from_uri(
    "gs://cloud-samples-data/vertex-ai/llm/prompts/landmark2.png",
    mime_type="image/png",
)
image_file3 = Part.from_uri(
    "gs://cloud-samples-data/vertex-ai/llm/prompts/landmark3.png",
    mime_type="image/png",
)

model = GenerativeModel(model_name="gemini-1.5-flash-001")
response = model.generate_content(
    [
        image_file1,
        "city: Rome, Landmark: the Colosseum",
        image_file2,
        "city: Beijing, Landmark: Forbidden City",
        image_file3,
    ]
)
print(response.text)

What's next

To search and filter code samples for other Google Cloud products, see the Google Cloud sample browser.