Image Resize API
Resizes an image to a target width/height under a chosen fit, returned base64-encoded.
- Endpoint
POST /v1/image-resize- Price
- $0.003 per call
- Family
- Images
01When to use it
- Resizing safely needs a real decoder and a hardened fetch: an agent that pulls the URL itself walks past every SSRF control, and the output must be byte-reproducible, which an ad-hoc resample is not.
When not to use it
- The input is over 25 MB (26,214,400 bytes): image-resize answers too_large (413).
- The destination needs more than 60 s to answer: the call ends with upstream_timeout (424).
- The destination is on a private or local network: the network guard refuses it with blocked_target (403).
02Parameters
| Field | Type | Required | Description |
|---|---|---|---|
| url | string | yes | Absolute http(s) URL of the source image, up to 2048 characters; redirects are followed, the bytes must be jpeg, png, gif, webp, tiff, avif, heic or svg by signature, and at most 40 megapixels. |
| width | integer | no | Target width in pixels, 1 to 20000; at least one of width or height is required, and a missing side follows the aspect ratio (except under fill). |
| height | integer | no | Target height in pixels, 1 to 20000; at least one of width or height is required, and a missing side follows the aspect ratio (except under fill). |
| fit | string | no | How the image fills the target box, as in sharp: inside fits within keeping the ratio (default), cover crops from the centre, contain pads to the full box, fill stretches, outside covers the box without cropping. One of: "cover", "contain", "fill", "inside", "outside". Default: "inside". |
| format | string | no | Output format; when omitted the source format is kept if it is png, jpeg or webp, otherwise the output is PNG. One of: "png", "jpeg", "webp". |
| quality | integer | no | Encoder quality from 1 to 100, default 80, used by the lossy jpeg and webp encoders and ignored for png. Default: 80. |
| allow_enlarge | boolean | no | When true the image may be scaled up past its native size; default false keeps each side at most its source size. Default: false. |
03Limits
| Limit | Value |
|---|---|
| Size cap | 25 MB (26,214,400 bytes) |
| Timeout | 60 s |
04Example
The published example of image-resize, verbatim: the request body and the response it returns.
Request
POST /v1/image-resize
content-type: application/json
payment-signature: <base64 x402 payload>
{
"url": "https://grist.tools/samples/images/tiles-64x40.png",
"width": 32,
"fit": "inside"
}Response
200 OK
payment-response: <base64 settlement receipt>
{
"source_url": "https://grist.tools/samples/images/tiles-64x40.png",
"source_format": "png",
"source_width": 64,
"source_height": 40,
"format": "png",
"mime_type": "image/png",
"fit": "inside",
"width": 32,
"height": 20,
"bytes": 779,
"image_base64": "iVBORw0KGgoAAAANSUhEUgAAACAAAAAUCAYAAADskT9PAAAACXBIWXMAAAsSAAAL..."
}Sample file: images/tiles-64x40.png.
In the sample itself: its IHDR chunk declares 64 by 40 pixels, 8-bit truecolour RGB with alpha and no interlacing. The chunks run IHDR, IDAT and IEND. In the returned file: its IHDR chunk declares 32 by 20 pixels, 8-bit truecolour RGB with alpha and no interlacing. The next chunk is pHYs.
| Response field | Type | In the example |
|---|---|---|
| source_url | string | "https://grist.tools/samples/images/tiles-64x40.png" |
| source_format | string | "png" |
| source_width | number | 64 |
| source_height | number | 40 |
| format | string | "png" |
| mime_type | string | "image/png" |
| fit | string | "inside" |
| width | number | 32 |
| height | number | 20 |
| bytes | number | 779 |
| image_base64 | string | a string of 67 characters |
05Call it from code
JavaScript
// image-resize: $0.003 per call, paid in USD Coin on eip155:8453 via x402
// Install: npm install @x402/fetch@2 @x402/evm@2 viem@2
// Save as client.mjs (ES module, Node 18+), export EVM_PRIVATE_KEY with the paying wallet's key in your shell, then run: node client.mjs
// The wrapper reads the 402 (payment-required), signs and retries with payment-signature.
import { wrapFetchWithPayment, x402Client, decodePaymentResponseHeader } from '@x402/fetch'
import { ExactEvmScheme } from '@x402/evm/exact/client'
import { privateKeyToAccount } from 'viem/accounts'
const account = privateKeyToAccount(process.env.EVM_PRIVATE_KEY)
const client = new x402Client().register('eip155:8453', new ExactEvmScheme(account))
const fetchWithPayment = wrapFetchWithPayment(fetch, client)
const body = {
"url": "https://grist.tools/samples/images/tiles-64x40.png",
"width": 32,
"fit": "inside"
}
const res = await fetchWithPayment('https://grist.tools/v1/image-resize', {
method: 'POST',
headers: { 'content-type': 'application/json' },
body: JSON.stringify(body),
})
console.log(res.status, await res.json())
const settle = res.headers.get('payment-response')
if (settle) console.log(decodePaymentResponseHeader(settle).transaction)Python
# image-resize: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# Install: pip install "x402[requests,evm]>=2.24,<3"
# The session reads the 402 (payment-required), signs and retries with payment-signature.
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http import decode_payment_response_header
from x402.http.clients.requests import x402_requests
from x402.mechanisms.evm.exact import register_exact_evm_client
from x402.mechanisms.evm.signers import EthAccountSigner
account = Account.from_key(os.environ["EVM_PRIVATE_KEY"])
client = x402ClientSync()
register_exact_evm_client(client, EthAccountSigner(account), networks="eip155:8453")
session = x402_requests(client)
payload = {
"url": "https://grist.tools/samples/images/tiles-64x40.png",
"width": 32,
"fit": "inside"
}
res = session.post("https://grist.tools/v1/image-resize", json=payload)
print(res.status_code, res.json())
settle = res.headers.get("payment-response")
if settle:
print(decode_payment_response_header(settle).transaction)curl
# image-resize: $0.003 per call, paid in USD Coin on eip155:8453 via x402
# 1. Unpaid call: HTTP 402, the requirements in the payment-required header (base64 JSON) and in the body.
curl -i -X POST 'https://grist.tools/v1/image-resize' -H 'content-type: application/json' -d '{"url":"https://grist.tools/samples/images/tiles-64x40.png","width":32,"fit":"inside"}'
# 2. Same call with the signed payment (an EIP-3009 authorization, EIP-712 signed: it cannot be
# typed by hand). x-payment is accepted as the v1 alternative. HTTP 200 carries payment-response.
curl -i -X POST 'https://grist.tools/v1/image-resize' -H 'content-type: application/json' -H 'payment-signature: <base64 x402 payload>' -d '{"url":"https://grist.tools/samples/images/tiles-64x40.png","width":32,"fit":"inside"}'06Errors
| Code | HTTP | For this service |
|---|---|---|
| invalid_input | 400 | The body does not match the schema; its fields are url, width, height, fit, format, quality and allow_enlarge. |
| blocked_target | 403 | |
| unreachable_target | 424 | |
| upstream_timeout | 424 | |
| unsupported_content_type | 415 | |
| too_large | 413 | |
| unprocessable | 422 | |
| internal | 500 |
Input that is rejected before the tool runs (malformed JSON, schema mismatch, body over the size limit) is never charged.
When each code is raised, and what it means for payment: /docs/image-resize.
07Questions
- How much does a image-resize call cost?
- $0.003 per call, paid in USDC on Base via x402, with no account and no API key.
- What does image-resize return?
- A JSON object with 11 top-level fields: source_url, source_format, source_width, source_height, format, mime_type, fit, width, height, bytes and image_base64. The example on this page is a real call over images/tiles-64x40.png.
- What happens when a image-resize call fails?
- The tool answers with a typed JSON error from the errors table. Payment is settled only after the tool has produced its result; a call that fails inside the tool is never settled. A 503 upstream_unavailable can follow a settled call; the x402 payments guide covers it, 429, 402 and an uncertain 500.