Method #runModel

examples/assets/src/index.ts:88–122

(prompt: string)

  // The model takes multipart form fields and returns the image as
  // a base64 string.
  async #runModel(prompt: string): Promise<Uint8Array> {
    const form = new FormData();
    form.append("prompt", prompt);
    form.append("width", "1024");
    form.append("height", "1024");

    // FormData doesn't expose its serialized body or boundary.
    // Passing it through a Response constructor serializes it and
    // sets the multipart Content-Type with the boundary the model
    // needs to parse the fields.
    const formResponse = new Response(form);
    const body = formResponse.body;
    const contentType = formResponse.headers.get("content-type");
    if (body === null || contentType === null) {
      throw new Error("failed to serialize the model request body");
    }

    // The model's multipart input shape isn't in the generated Ai
    // types yet, so call run() through a minimal typed view of the
    // binding. Keep the call on env.AI: the binding's run() is a
    // method that relies on its own `this`, so a detached reference
    // would throw inside the binding.
    const ai = this.env.AI as unknown as {
      run(
        model: string,
        input: { multipart: { body: ReadableStream; contentType: string } },
      ): Promise<{ image?: string }>;
    };
    const result = await ai.run(IMAGE_MODEL, { multipart: { body, contentType } });

    if (typeof result.image !== "string") {
      throw new Error("image model returned no image");
    }
    return decodeBase64(result.image);
  }
}

export default {