How to Use the Seedream 4.0 API: image to image integration guide (2026)

Seedream 4.0 is an image to image model by Doubao: Seedream 4.0: 4K image generation and editing with character and object consistency and sequential multi-image outputs. Ready-to-use REST inference API, best performance, no coldstarts, affordable pricing. On NamiFusion you can try it in the playground (exact quote shown before you submit), then call it through one unified REST API — a typical run costs about $0.030.

TL;DR

· Task type: image to image, provided by Doubao

· Pricing: about $0.030 per typical run ($1 = 100 credits), pay-as-you-go

· Getting started: playground (exact quote before submit) → create an API key → one POST request

· Tunable parameters: 4 (see the table below)

· No platform watermark; commercial use allowed (per the Terms of Service)

What can you build with Seedream 4.0?

Social media visuals and covers: batch-generate on-theme images and schedule them straight away.

E-commerce and ad creatives: product scenes, banner backgrounds, and multi-variant visuals for A/B tests.

Concept art and ideation: characters, environments and style boards, iterated cheaply and fast.

Pipeline chaining: outputs feed directly into image-to-video or face swap as source material.

How do you call this API?

1. Sign up on NamiFusion and create a key on the API Keys page (free credits on signup).

2. Submit a task with the cURL example below, passing your key as a Bearer token.

3. Poll the task status with the returned task_uuid and read the output URLs when completed.

# 1) Submit — returns { "task_uuid": "..." }
curl -X POST "https://www.namifusion.com/api/v1/marketplace/run/doubao/seedream-4.0/image-to-image-sequential" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "input": {
    "images": [
      "https://assets-public.namifusion.com/uploads/images/2026-04-21/04f96c6016ee.png",
      "https://assets-public.namifusion.com/uploads/images/2026-04-21/ee16c2ba0571.png"
    ],
    "prompt": "Generate a 4K image of a futuristic cityscape with sleek skyscrapers, flying cars, and glowing neon lights. Please generate a set of 5 images.",
    "size": "3840x2160",
    "max_images": 5
  }
}'

# 2) Poll until status is "completed", then read the output URLs
curl "https://www.namifusion.com/api/v1/marketplace/run/tasks/TASK_UUID" \
  -H "Authorization: Bearer YOUR_API_KEY"

What parameters does it take?

images (Images): required

prompt (Prompt): required

size (Size): optional

max_images (Max Images): optional, default 1

How do you write prompts for Seedream 4.0?

1. Subject first: lead with the actor and action, then add environment, lighting and style ("an astronaut sprinting through a neon street in the rain, cinematic, shallow depth of field").

2. Concrete nouns beat stacked adjectives: "85mm portrait lens, golden-hour backlight" works far better than "very beautiful, ultra high quality".

3. Change one variable per iteration: pin the seed to reproduce a result, tweak a single phrase at a time so you know what actually moved the output.

4. State negatives positively: instead of "no blur", ask for "sharp focus, crisp details".

How much does it cost?

Pay-per-use in credits. A typical run costs about $0.030 ($1 = 100 credits); the exact price varies with parameters like resolution or duration, and the playground shows the exact quote before you submit.