Image Editing API (img2img)

Edit existing images — pass one or more source images and describe what to change.

Two request formats are accepted

application/json — image as a data:image/...;base64,… string, or a JSON array of them for multi-image fusion. (BlockRun-native.)
multipart/form-data — OpenAI's format: repeated image[]=@file fields (plus mask, model, prompt, size, n). Files are converted internally.

Payment is always x402 (the X-Payment / PAYMENT-SIGNATURE header), regardless of body format. So you can send an OpenAI-shaped multipart body, but you still attach an x402 payment — the OpenAI SDK's native Bearer-key auth does not settle payment here. Use the BlockRun SDK / ClawRouter (which handle x402), or send either body format with your own x402 header.

Endpoint

Network	URL
Base	`https://blockrun.ai/api/v1/images/image2image`
Solana	`https://sol.blockrun.ai/api/v1/images/image2image`

POST https://blockrun.ai/api/v1/images/image2image       # Base
POST https://sol.blockrun.ai/api/v1/images/image2image    # Solana

Request

{
  "model": "openai/gpt-image-1",
  "prompt": "change the background to a starry sky",
  "image": "data:image/png;base64,<base64-data>",
  "mask": "data:image/png;base64,<base64-data>",
  "size": "1024x1024",
  "n": 1
}

Parameters

Parameter	Type	Required	Description
`model`	string	No	Model to use (default: `openai/gpt-image-2`). Supported: `openai/gpt-image-1`, `openai/gpt-image-2`, `google/nano-banana`, `google/nano-banana-pro`
`prompt`	string	Yes	Description of edits to make
`image`	string \| string[]	Yes	Source image as a base64 data URI, or an array of data URIs to fuse multiple sources into one variant (e.g. a reference image + a brand logo). OpenAI-compatible `image[]`. Max 4 images for OpenAI, 3 for Google.
`mask`	string	No	Mask image as base64 data URI (white = area to edit). Single-image only — cannot be combined with a multi-image `image[]` array.
`size`	string	No	Output size (default: `1024x1024`)
`n`	integer	No	Number of images to generate (default: 1)

Supported Models

Model ID	Provider	Mask	Sizes	Pricing
`openai/gpt-image-1`	OpenAI	✅	1024x1024, 1536x1024, 1024x1536	$0.02-0.04
`openai/gpt-image-2`	OpenAI	✅	1024x1024, 1536x1024, 1024x1536	$0.06-0.12
`google/nano-banana`	Google (Gemini 2.5 Flash Image)	❌ prompt-only	1024x1024	$0.05
`google/nano-banana-pro`	Google (Gemini 3 Pro Image)	❌ prompt-only	1024x1024, 2048x2048, 4096x4096	$0.10-0.15

Hybrid sync/async flow & settlement

Like /v1/images/generations, this endpoint is hybrid — it is not always synchronous:

Fast edits (≤30s inline window): 200 with the standard { created, data: [...] } body below. Payment settles inside this response.
Slow edits (>30s — multi-image gpt-image-2 fusion routinely takes longer): 202 with an async job envelope { id, status, poll_url, price, payment_status: "verified" }. Nothing has been charged yet. Poll GET {poll_url} (it lives under /v1/images/generations/{id} — edits share the same job store) with an x-payment header from the same wallet every 2–5s. USDC settles exactly once, on the first poll that observes status: "completed". A job that ends failed, or that you never poll, is never charged.

No charge until the image is ready

On the slow async path nothing is debited at submit time (payment_status: "verified"). USDC settles exactly once — on the first poll that sees status: "completed". Failed jobs and never-polled jobs are never charged.

The envelope fields, poll responses, status enum (queued → in_progress → completed | failed) and settlement guarantees are identical to image generation — see the full spec there. Go SDK blockrun-llm-go ≥ v0.17.0 (ImageClient.Edit) handles the hybrid flow transparently and always returns the synchronous shape.

Response

{
  "created": 1706000000,
  "data": [
    {
      "url": "https://...",
      "revised_prompt": "A photo with the background changed to..."
    }
  ],
  "price": { "amount": "0.063000", "currency": "USD" },
  "payment": { "status": "settled", "tx_hash": "0x…", "network": "base" }
}

Response Fields

Field	Type	Description
`created`	integer	Unix timestamp
`data`	array	Array of edited images
`data[].url`	string	URL to edited image
`data[].revised_prompt`	string	Expanded prompt
`price.amount`	string	USD charged for this call
`payment.status`	string	`settled` \| `already_settled`
`payment.tx_hash`	string	On-chain USDC settlement tx (also in `X-Payment-Receipt` header)

Examples

Via ClawRouter (recommended)

The easiest way is using ClawRouter's /img2img slash command, which reads local files automatically:

/img2img --image ~/photo.png change the background to a starry sky
/img2img --image ./cat.jpg --mask ./mask.png remove the background
/img2img --image /tmp/portrait.png --size 1536x1024 add a hat

Via ClawRouter API

ClawRouter handles x402 payments automatically:

# First, convert your image to base64
IMAGE_B64=$(base64 -i ~/photo.png)

curl -X POST http://localhost:8402/v1/images/image2image \
  -H "Content-Type: application/json" \
  -d "{
    \"model\": \"openai/gpt-image-1\",
    \"prompt\": \"change the background to a starry sky\",
    \"image\": \"data:image/png;base64,${IMAGE_B64}\",
    \"size\": \"1024x1024\"
  }"

Direct API (cURL)

IMAGE_B64=$(base64 -i ~/photo.png)

# Base
curl -X POST https://blockrun.ai/api/v1/images/image2image \
  -H "Content-Type: application/json" \
  -H "X-Payment: $PAYMENT_HEADER" \
  -d "{
    \"model\": \"openai/gpt-image-1\",
    \"prompt\": \"change the background to a starry sky\",
    \"image\": \"data:image/png;base64,${IMAGE_B64}\",
    \"size\": \"1024x1024\"
  }"

# Solana
curl -X POST https://sol.blockrun.ai/api/v1/images/image2image \
  -H "Content-Type: application/json" \
  -H "X-Payment: $PAYMENT_HEADER" \
  -d "{
    \"model\": \"openai/gpt-image-1\",
    \"prompt\": \"change the background to a starry sky\",
    \"image\": \"data:image/png;base64,${IMAGE_B64}\",
    \"size\": \"1024x1024\"
  }"

Mask Usage

Mask is OpenAI-only

Masks apply to openai/gpt-image-1 and openai/gpt-image-2. Google nano-banana / nano-banana-pro are prompt-only — passing a mask to a Google model returns 400.

The mask defines which parts of the image to edit:

White pixels = areas to edit (AI generates new content here)
Black pixels = areas to keep unchanged

If no mask is provided, the AI will edit the entire image based on the prompt.

Multi-image input (image fusion)

Pass an array of source images in image to fuse several inputs into one result — e.g. a reference image + a brand logo, composed by a single prompt.

OpenAI gpt-image-1 / gpt-image-2: up to 4 source images.
Google nano-banana / nano-banana-pro: up to 3 source images (earlier images act as primary composition anchors).
mask cannot be combined with a multi-image array (mask is single-region only) → 400.
Exceeding a provider's image cap → 400.

Two ways to send multiple images

JSON (shown below): image as a JSON array of base64 data URIs.
Multipart (OpenAI's format): repeated image[]=@file fields, e.g. -F "image[]=@ref.png" -F "image[]=@logo.png".

Both are accepted. Payment is still x402 in either case (see the format note at the top).

REF_B64=$(base64 -i ~/reference-post.png)
LOGO_B64=$(base64 -i ~/brand-logo.png)

curl -X POST https://blockrun.ai/api/v1/images/image2image \
  -H "Content-Type: application/json" \
  -H "X-Payment: $PAYMENT_HEADER" \
  -d "{
    \"model\": \"google/nano-banana\",
    \"prompt\": \"place the brand logo in the corner, vintage warm palette, no text overlay\",
    \"image\": [
      \"data:image/png;base64,${REF_B64}\",
      \"data:image/png;base64,${LOGO_B64}\"
    ],
    \"size\": \"1024x1024\"
  }"

Same request in OpenAI multipart format (repeated image[]):

curl -X POST https://blockrun.ai/api/v1/images/image2image \
  -H "X-Payment: $PAYMENT_HEADER" \
  -F "model=google/nano-banana" \
  -F "prompt=place the brand logo in the corner, vintage warm palette, no text overlay" \
  -F "image[]=@reference-post.png" \
  -F "image[]=@brand-logo.png" \
  -F "size=1024x1024"

Single-image requests are unchanged — image as a plain string (JSON) or a single image[]/image file (multipart) both work.

Pricing

Prices include 5% BlockRun margin:

Model	Size	Price
GPT Image 1	1024x1024	$0.021
GPT Image 1	1536x1024	$0.042
GPT Image 1	1024x1536	$0.042
ChatGPT Images 2.0	1024x1024	$0.063
ChatGPT Images 2.0	1536x1024	$0.126
ChatGPT Images 2.0	1024x1536	$0.126
Nano Banana	1024x1024	$0.0525
Nano Banana Pro	1024x1024	$0.105
Nano Banana Pro	2048x2048	$0.105
Nano Banana Pro	4096x4096	$0.1575

Error Codes

Code	Description
400	Invalid request (bad image format, unsupported model, invalid size)
402	Payment required
429	Rate limit exceeded
500	Server error
504	Image editing timed out

What's next?

Image Generation

Generate images from a text prompt with the same model lineup and hybrid settlement flow.

ClawRouter

The /img2img slash command reads local files and handles x402 payments for you.