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tessl/maven-dev-langchain4j--langchain4j-vertex-ai

LangChain4j integration for Google Vertex AI models including chat, language, embedding, image, and scoring capabilities

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examples.mddocs/models/image/

Image Model Examples

Basic Image Generation

import dev.langchain4j.model.vertexai.VertexAiImageModel;
import dev.langchain4j.data.image.Image;
import dev.langchain4j.model.output.Response;

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .build();

Response<Image> response = model.generate("A serene mountain landscape at sunset");
Image image = response.content();

// Access image data
byte[] imageData = image.bytes();
String base64Data = image.base64Data();
URI imageUri = image.uri();

Generate Multiple Variations

Response<List<Image>> response = model.generate(
    "A futuristic city with flying cars",
    4  // Generate 4 variations
);

List<Image> images = response.content();
for (int i = 0; i < images.size(); i++) {
    System.out.println("Image " + i + " URI: " + images.get(i).uri());
}

With Generation Parameters

import dev.langchain4j.model.vertexai.VertexAiImageModel.AspectRatio;
import dev.langchain4j.model.vertexai.VertexAiImageModel.MimeType;
import dev.langchain4j.model.vertexai.VertexAiImageModel.PersonGeneration;

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .aspectRatio(AspectRatio.LANDSCAPE)          // 16:9 aspect ratio
    .seed(12345L)                                 // Reproducible results
    .guidanceScale(15)                            // Edit strength
    .negativePrompt("blurry, low quality")        // What to avoid
    .mimeType(MimeType.PNG)                       // PNG format
    .personGeneration(PersonGeneration.ALLOW_ADULT)
    .maxRetries(3)
    .build();

Reproducible Generation (Seed)

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .seed(42L)  // Same seed = same image for same prompt
    .build();

Response<Image> response1 = model.generate("A red apple");
Response<Image> response2 = model.generate("A red apple");
// response1 and response2 will produce identical images

With Negative Prompt

String prompt = "A professional photograph of a modern office space";
String negativePrompt = "blurry, dark, cluttered, distorted, low quality";

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .negativePrompt(negativePrompt)
    .build();

Response<Image> response = model.generate(prompt);

Aspect Ratios

// Square (1:1)
VertexAiImageModel squareModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .aspectRatio(AspectRatio.SQUARE)
    .build();

// Portrait (9:16)
VertexAiImageModel portraitModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .aspectRatio(AspectRatio.PORTRAIT)
    .build();

// Landscape (16:9)
VertexAiImageModel landscapeModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .aspectRatio(AspectRatio.LANDSCAPE)
    .build();

Output Format (PNG vs JPEG)

// PNG (lossless, larger files)
VertexAiImageModel pngModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .mimeType(MimeType.PNG)
    .build();

// JPEG (lossy, smaller files)
VertexAiImageModel jpegModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .mimeType(MimeType.JPEG)
    .compressionQuality(85)  // 1-100, higher = better quality
    .build();

Local Persistence

import java.nio.file.Path;

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .withPersisting()
    .persistTo(Path.of("/path/to/save/images"))
    .build();

Response<Image> response = model.generate("A sunset");
// Image automatically saved to /path/to/save/images/

Cloud Storage Persistence

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .persistToCloudStorage("gs://my-bucket/images/")
    .build();

Response<Image> response = model.generate("A mountain");
// Image automatically saved to gs://my-bucket/images/

Edit Image with Prompt

import java.nio.file.Files;
import java.nio.file.Path;

Image sourceImage = Image.fromBytes(
    Files.readAllBytes(Path.of("input.png"))
);

Response<Image> response = model.edit(
    sourceImage,
    "Add a rainbow in the sky"
);

Image editedImage = response.content();

Edit Image with Mask

Image sourceImage = Image.fromBytes(
    Files.readAllBytes(Path.of("input.png"))
);
Image maskImage = Image.fromBytes(
    Files.readAllBytes(Path.of("mask.png"))  // White = edit, Black = preserve
);

Response<Image> response = model.edit(
    sourceImage,
    maskImage,
    "Replace masked area with a lake"
);

Image editedImage = response.content();

Person Generation Policy

// Don't generate people
VertexAiImageModel noPersonModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .personGeneration(PersonGeneration.DONT_ALLOW)
    .build();

// Allow adults only
VertexAiImageModel adultModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .personGeneration(PersonGeneration.ALLOW_ADULT)
    .build();

Image Styles (Imagen v1 only)

import dev.langchain4j.model.vertexai.VertexAiImageModel.ImageStyle;

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@002")  // Imagen v1
    .sampleImageStyle(ImageStyle.WATERCOLOR)
    .build();

Response<Image> response = model.generate("A forest scene");

Guidance Scale (Edit Strength)

// Low guidance (subtle changes)
VertexAiImageModel subtleModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .guidanceScale(5)  // 0-9: subtle
    .build();

// High guidance (strong changes)
VertexAiImageModel strongModel = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .guidanceScale(25)  // 21+: strong
    .build();

Language Support

VertexAiImageModel model = VertexAiImageModel.builder()
    .endpoint("https://us-central1-aiplatform.googleapis.com/v1/")
    .project("your-project-id")
    .location("us-central1")
    .publisher("google")
    .modelName("imagegeneration@006")
    .language("es")  // Spanish
    .build();

Response<Image> response = model.generate("Una montaña hermosa");

Save Image to File

Response<Image> response = model.generate("A sunset");
Image image = response.content();

// Save to file
Files.write(Path.of("generated-image.png"), image.bytes());

Error Handling

try {
    Response<Image> response = model.generate("Some prompt");
    Image image = response.content();
} catch (Exception e) {
    System.err.println("Image generation failed: " + e.getMessage());
    // Model automatically retries transient errors up to maxRetries
}

Prompt Best Practices

// Good: Descriptive and specific
String goodPrompt = "A professional photograph of a modern office space, " +
                    "natural lighting, minimalist design, wide angle, " +
                    "high detail, 4k quality";

// Include style, lighting, composition
String detailedPrompt = "Digital art, cyberpunk city at night, " +
                        "neon lights, rain-soaked streets, " +
                        "cinematic composition, vibrant colors";

// Use negative prompt for quality
String negativePrompt = "blurry, distorted, low quality, watermark, " +
                        "text, signature, deformed";

Install with Tessl CLI

npx tessl i tessl/maven-dev-langchain4j--langchain4j-vertex-ai@1.11.0

docs

models

image

api.md

examples.md

overview.md

index.md

quick-reference.md

tile.json