Stable Diffusion 3.0 (SD3) image-to-image code example

generate.ts

import FormData from "form-data";
import fs from "node:fs";
import axios from "axios";

export async function generate(
  originalImagePath: string,
  resultImageName: string,
  prompt: string,
  negativePrompt: string,
  strength: number,
): Promise<string> {
  const apiHost = "https://api.stability.ai";
  const apiKey = "sk-**********************";

  if (!apiKey) throw new Error("Missing Stability API key.");

  const image = fs.createReadStream(originalImagePath);
  const formData = new FormData();

  formData.append("mode", "image-to-image");
  formData.append("model", "sd3"); // or sd3-turbo
  formData.append("image", image);
  formData.append("prompt", prompt);
  formData.append("strength", String(strength));
  formData.append("negative_prompt", negativePrompt); // NOT work with sd3-turbo
  formData.append("seed", "0");
  formData.append("output_format", "png");

  const response = await axios.post(
    `${apiHost}/v2beta/stable-image/generate/sd3`,
    formData,
    {
      headers: {
        Authorization: `Bearer ${apiKey}`,
        ...formData.getHeaders(),
      },
      responseType: "json",
    },
  );

  const json = response.data;

  if (response.status === 200 && "finish_reason" in json) {
    if (json.finish_reason === "SUCCESS") {
      const imageData = json.image;
      if (!imageData) {
        throw new Error("Image data not found in the response.");
      }
      const fp = `./data/${resultImageName}.png`;
      fs.writeFileSync(fp, Buffer.from(imageData, "base64"));
      return fp;
    }
    throw new Error(json.finish_reason);
  }
  throw new Error(`Unknown generation error: ${JSON.stringify(json)}`);
}