invokeModel.js

// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

// snippet-start:[javascript.v3.bedrock-runtime.InvokeModel_AmazonNovaImageGeneration]

import {
  BedrockRuntimeClient,
  InvokeModelCommand,
} from "@aws-sdk/client-bedrock-runtime";
import { saveImage } from "../../utils/image-creation.js";
import { fileURLToPath } from "node:url";

/**
 * This example demonstrates how to use Amazon Nova Canvas to generate images.
 * It shows how to:
 * - Set up the Amazon Bedrock runtime client
 * - Configure the image generation parameters
 * - Send a request to generate an image
 * - Process the response and handle the generated image
 *
 * @returns {Promise<string>} Base64-encoded image data
 */
export const invokeModel = async () => {
  // Step 1: Create the Amazon Bedrock runtime client
  // Credentials will be automatically loaded from the environment
  const client = new BedrockRuntimeClient({ region: "us-east-1" });

  // Step 2: Specify which model to use
  // For the latest available models, see:
  // https://docs.aws.amazon.com/bedrock/latest/userguide/models-supported.html
  const modelId = "amazon.nova-canvas-v1:0";

  // Step 3: Configure the request payload
  // First, set the main parameters:
  // - prompt: Text description of the image to generate
  // - seed: Random number for reproducible generation (0 to 858,993,459)
  const prompt = "A stylized picture of a cute old steampunk robot";
  const seed = Math.floor(Math.random() * 858993460);

  // Then, create the payload using the following structure:
  // - taskType: TEXT_IMAGE (specifies text-to-image generation)
  // - textToImageParams: Contains the text prompt
  // - imageGenerationConfig: Contains optional generation settings (seed, quality, etc.)
  // For a list of available request parameters, see:
  // https://docs.aws.amazon.com/nova/latest/userguide/image-gen-req-resp-structure.html
  const payload = {
    taskType: "TEXT_IMAGE",
    textToImageParams: {
      text: prompt,
    },
    imageGenerationConfig: {
      seed,
      quality: "standard",
    },
  };

  // Step 4: Send and process the request
  // - Embed the payload in a request object
  // - Send the request to the model
  // - Extract and return the generated image data from the response
  try {
    const request = {
      modelId,
      body: JSON.stringify(payload),
    };
    const response = await client.send(new InvokeModelCommand(request));

    const decodedResponseBody = new TextDecoder().decode(response.body);
    // The response includes an array of base64-encoded PNG images
    /** @type {{images: string[]}} */
    const responseBody = JSON.parse(decodedResponseBody);
    return responseBody.images[0]; // Base64-encoded image data
  } catch (error) {
    console.error(`ERROR: Can't invoke '${modelId}'. Reason: ${error.message}`);
    throw error;
  }
};

// If run directly, execute the example and save the generated image
if (process.argv[1] === fileURLToPath(import.meta.url)) {
  console.log("Generating image. This may take a few seconds...");
  invokeModel()
    .then(async (imageData) => {
      const imagePath = await saveImage(imageData, "nova-canvas");
      // Example path: javascriptv3/example_code/bedrock-runtime/output/nova-canvas/image-01.png
      console.log(`Image saved to: ${imagePath}`);
    })
    .catch((error) => {
      console.error("Execution failed:", error);
      process.exitCode = 1;
    });
}
// snippet-end:[javascript.v3.bedrock-runtime.InvokeModel_AmazonNovaImageGeneration]