FLUX.1 [dev] Image to Image API Docs | fal

fal-ai/flux/dev/image-to-image

Image to Image [dev]

FLUX.1 Image-to-Image is a high-performance endpoint for the FLUX.1 [dev] model that enables rapid transformation of existing images, delivering high-quality style transfers and image modifications with the core FLUX capabilities.

Table of contents

About

Image to image version of FLUX.1 [dev], next generation image-to-image model.

1. Calling the API

Install the client

The client provides a convenient way to interact with the model API.

npm install --save @fal-ai/client

Migrate to @fal-ai/client

The @fal-ai/serverless-client package has been deprecated in favor of @fal-ai/client. Install the new package and update your imports.

Setup your API Key

Set FAL_KEY as an environment variable in your runtime.

export FAL_KEY="YOUR_API_KEY"

Submit a request

The client API handles the API submit protocol. It will handle the request status updates and return the result when the request is completed.

import { fal } from "@fal-ai/client";

const result = await fal.subscribe("fal-ai/flux/dev/image-to-image", {
  input: {
    image_url: "https://fal.media/files/koala/Chls9L2ZnvuipUTEwlnJC.png",
    prompt: "A cat dressed as a wizard with a background of a mystic forest."
  },
  logs: true,
  onQueueUpdate: (update) => {
    if (update.status === "IN_PROGRESS") {
      update.logs.map((log) => log.message).forEach(console.log);
    }
  },
});
console.log(result.data);
console.log(result.requestId);

2. Authentication

The API uses an API Key for authentication. It is recommended you set the FAL_KEY environment variable in your runtime when possible.

API Key

In case your app is running in an environment where you cannot set environment variables, you can set the API Key manually as a client configuration.

import { fal } from "@fal-ai/client";

fal.config({
  credentials: "YOUR_FAL_KEY"
});
Protect your API Key

When running code on the client-side (e.g. in a browser, mobile app or GUI applications), make sure to not expose your FAL_KEY. Instead, use a server-side proxy to make requests to the API.

3. Queue

Long-running requests

For long-running requests, such as training jobs or models with slower inference times, it is recommended to check the Queue status and rely on Webhooks instead of blocking while waiting for the result.

Submit a request

The client API provides a convenient way to submit requests to the model.

import { fal } from "@fal-ai/client";

const { request_id } = await fal.queue.submit("fal-ai/flux/dev/image-to-image", {
  input: {
    image_url: "https://fal.media/files/koala/Chls9L2ZnvuipUTEwlnJC.png",
    prompt: "A cat dressed as a wizard with a background of a mystic forest."
  },
  webhookUrl: "https://optional.webhook.url/for/results",
});

Fetch request status

You can fetch the status of a request to check if it is completed or still in progress.

import { fal } from "@fal-ai/client";

const status = await fal.queue.status("fal-ai/flux/dev/image-to-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b",
  logs: true,
});

Get the result

Once the request is completed, you can fetch the result. See the Output Schema for the expected result format.

import { fal } from "@fal-ai/client";

const result = await fal.queue.result("fal-ai/flux/dev/image-to-image", {
  requestId: "764cabcf-b745-4b3e-ae38-1200304cf45b"
});
console.log(result.data);
console.log(result.requestId);

4. Files

Some attributes in the API accept file URLs as input. Whenever that's the case you can pass your own URL or a Base64 data URI.

Data URI (base64)

You can pass a Base64 data URI as a file input. The API will handle the file decoding for you.

Hosted files (URL)

You can also pass your own URLs as long as they are publicly accessible.

Uploading files

We provide a convenient file storage that allows you to upload files and use them in your requests.

import { fal } from "@fal-ai/client";

const file = new File(["Hello, World!"], "hello.txt", { type: "text/plain" });
const url = await fal.storage.upload(file);

5. Schema

Input

{
  "image_url": "https://fal.media/files/koala/Chls9L2ZnvuipUTEwlnJC.png",
  "strength": 0.95,
  "num_inference_steps": 40,
  "prompt": "A cat dressed as a wizard with a background of a mystic forest.",
  "guidance_scale": 3.5,
  "num_images": 1,
  "enable_safety_checker": true,
  "output_format": "jpeg",
  "acceleration": "none"
}

Output

{
  "images": [
    {
      "url": "",
      "content_type": "image/jpeg"
    }
  ],
  "prompt": ""
}

Other types

Image