On-the-fly Image Proxy: Resize

What it does

On-the-fly Image Proxy: Resize, compress, crop, and convert remote images (JPEG, PNG, WebP, AVIF, GIF) with sharp

Request

Body

Field	Type	Required	Description
`blur`	number	no	Apply Gaussian blur sigma value
`fit`	enum	no	Resize fit strategy One of: cover, contain, fill, inside, outside.
`format`	enum	no	Target output format One of: webp, jpeg, png, avif, gif.
`grayscale`	boolean	no	Convert image to black and white
`height`	integer	no	Target image height in pixels
`imageUrl`	string	yes
`quality`	integer	no	Compression quality percentage
`returnBinary`	boolean	no	If true, returns raw image bytes stream. If false, returns JSON with Base64 Data URI & rich metadata.
`rotate`	enum	no	Rotation angle in degrees One of: 0, 90, 180, 270.
`width`	integer	no	Target image width in pixels

Example request

{
  "blur": 5.1,
  "fit": "cover",
  "format": "webp",
  "grayscale": false,
  "height": 630,
  "imageUrl": "https://example.com/page",
  "quality": 80,
  "returnBinary": false,
  "rotate": 0,
  "width": 1200
}

Response

Field	Type	Description
`dataUri`	string
`metadata`	object
`↳ channels`	integer
`↳ compressionSavingsPercent`	string
`↳ format`	string
`↳ height`	integer
`↳ postTransformSizeBytes`	integer
`↳ preTransformSizeBytes`	integer
`↳ width`	integer
`sourceUrl`	string
`status`	string
`tokensDeducted`	integer

Example response

{
  "dataUri": "<data uri>",
  "metadata": {
    "channels": 19,
    "compressionSavingsPercent": "42.5",
    "format": "json",
    "height": 630,
    "postTransformSizeBytes": 9,
    "preTransformSizeBytes": 40,
    "width": 1200
  },
  "sourceUrl": "https://example.com/page",
  "status": "success",
  "tokensDeducted": 1
}

Errors

Every error answers with the same envelope: an HTTP status, a machine code and a sentence.

`400`	The body or a parameter failed validation. The details array names the field.
`401`	No key, a revoked key or a wrong header. Send x-api-key.
`402`	The wallet cannot cover this call. Top up or wait for the monthly grant.
`404`	The resource does not exist, or it is not yours. Both answer identically and cost nothing.
`429`	Over the per-minute quota of your tier. Back off and retry.
`5xx`	Upstream refused or timed out. The call is not billed.

Code

curl -X POST 'https://app.castomapi.com/v1/proxy/image-transform' \
  -H 'x-api-key: <your-api-key>' \
  -H 'Content-Type: application/json' \
  -d '{"blur": 5.1, "fit": "cover", "format": "webp", "grayscale": false, "height": 630, "imageUrl": "https://example.com/page", "quality": 80, "returnBinary": false, "rotate": 0, "width": 1200}'

const res = await fetch('https://app.castomapi.com/v1/proxy/image-transform', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"blur": 5.1, "fit": "cover", "format": "webp", "grayscale": false, "height": 630, "imageUrl": "https://example.com/page", "quality": 80, "returnBinary": false, "rotate": 0, "width": 1200})
});
const data = await res.json();
console.log(data);

import { request } from 'node:https';

// Node 18+ has fetch built in
const res = await fetch('https://app.castomapi.com/v1/proxy/image-transform', {
  method: 'POST',
  headers: { 'x-api-key': '<your-api-key>', 'Content-Type': 'application/json' },
  body: JSON.stringify({"blur": 5.1, "fit": "cover", "format": "webp", "grayscale": false, "height": 630, "imageUrl": "https://example.com/page", "quality": 80, "returnBinary": false, "rotate": 0, "width": 1200})
});
const data = await res.json();
console.log(data);

import requests

res = requests.post(
    'https://app.castomapi.com/v1/proxy/image-transform',
    headers={'x-api-key': '<your-api-key>'},
    json={"blur": 5.1, "fit": "cover", "format": "webp", "grayscale": False, "height": 630, "imageUrl": "https://example.com/page", "quality": 80, "returnBinary": False, "rotate": 0, "width": 1200},
    timeout=30,
)
print(res.json())

<?php
$ch = curl_init('https://app.castomapi.com/v1/proxy/image-transform');
curl_setopt_array($ch, [
    CURLOPT_CUSTOMREQUEST => 'POST',
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['x-api-key: <your-api-key>', 'Content-Type: application/json'],
    CURLOPT_POSTFIELDS => json_encode(['blur' => 5.1, 'fit' => 'cover', 'format' => 'webp', 'grayscale' => false, 'height' => 630, 'imageUrl' => 'https://example.com/page', 'quality' => 80, 'returnBinary' => false, 'rotate' => 0, 'width' => 1200]),
]);
$data = json_decode(curl_exec($ch), true);
print_r($data);

Cost and limits

This operation costs 1 token. A call that fails is never billed. Every account gets 1000 free tokens a month; paid balances never expire.

Rate limits per minute

No key	10
Free	60
Pro	300
Enterprise	1200

Docs → Pricing

Questions

What does On-the-fly Image Proxy: Resize cost?

1 token per successful call, debited from your wallet after the response. Failed calls are free. Every account receives 1000 free tokens a month.

How do I authenticate?

Send your key in the x-api-key header. One key covers every metered endpoint; there is nothing to enable per endpoint.

Can I send an Authorization: Bearer token instead?

Not for a metered endpoint — those take the x-api-key header and nothing else. Bearer tokens belong to the account side: the dashboard and account APIs accept a JWT session, and castomapi-auth issues those through a standard OAuth2 handshake, with authorization code, client credentials and refresh grants. The auth service page covers it.

What are the limits?

10 requests a minute per IP with no key at all, 60 a minute on the free tier, 300 on Pro, 1200 on Enterprise. Above the no-key tier the quota is per account, across every endpoint.

OpenAPI: https://app.castomapi.com/docs/json

Request

Response

What it does

Request

Body

Example request

Response

Example response

Errors

Code

Cost and limits

Rate limits per minute

Questions

More in Proxy

Where it fits