Watermark & AIGC Labeling

Add Image Watermark

0calls

5 credits / call

Want to brand your original images without spoiling how they look, or trace AIGC-generated images later on? This endpoint quietly tucks a marker of your choosing inside the image.

POST

uapis.cn

/api/v1/watermark/embed

Body

file

The image file to watermark. PNG, JPEG, and WebP are supported.

Drag a file here, orclick to upload

The image file to watermark. PNG, JPEG, and WebP are supported.

url

string

An image link that's publicly reachable.

image_base64

string

The image as Base64; the data: prefix is optional.

payload

string

required

The marker to write into the image; what goes in is up to you.

out_format

string

Output image format. Leave empty to match the input.

jpeg_quality

integer

Image quality for JPEG output, 1 to 100.

ecc

string

Error-correction level. It sets how much damage the watermark can survive and how many characters fit: stronger correction survives compression and cropping better but fits fewer characters. Defaults to `BCH_4`.

model_type

string

Watermark profile that trades robustness against image quality. Defaults to `B`.

strength

number

Watermark strength, defaults to 1.0. Higher survives compression and reposting better but is more likely to be visible; lower is more discreet but less robust.

Overview

You upload an image and give it a marker, and the endpoint embeds that text invisibly into the image's pixels. The result looks no different to the eye, yet it holds up against common resizing, cropping, social-platform compression, and re-forwarding. It's a good fit for marking where an image came from, tracking distribution channels, or quietly asserting copyright.

Notes

Capacity: by the nature of invisible watermarking, only a limited number of characters fit in an image (usually a short code). Store just a short provenance ID or signature, and keep the full mapping in your own database.

Parameters: provide the image one of three ways (file / url / image_base64); unless you have a specific need, leave the other advanced parameters empty to use the best-practice defaults.

Request body

Image source and watermark content. Both multipart/form-data and application/json are supported.

file

fileoptional

The image file to watermark. PNG, JPEG, and WebP are supported.

url

stringoptional

An image link that's publicly reachable.

image_base64

stringoptional

The image as Base64; the data: prefix is optional.

payload

stringrequired

The marker to write into the image; what goes in is up to you.

out_format

stringoptional

Output image format. Leave empty to match the input.

jpeg_quality

integeroptional

Image quality for JPEG output, 1 to 100.

ecc

stringoptional

model_type

stringoptional

Watermark profile that trades robustness against image quality. Defaults to `B`.

strength

numberoptional

Watermark strength, defaults to 1.0. Higher survives compression and reposting better but is more likely to be visible; lower is more discreet but less robust.

Name	Type	Attributes	Description
`file`	file	optional	The image file to watermark. PNG, JPEG, and WebP are supported.
`url`	string	optional	An image link that's publicly reachable.
`image_base64`	string	optional	The image as Base64; the data: prefix is optional.
`payload`	string	required	The marker to write into the image; what goes in is up to you.
`out_format`	string	optional	Output image format. Leave empty to match the input.
`jpeg_quality`	integer	optional	Image quality for JPEG output, 1 to 100.
`ecc`	string	optional	Error-correction level. It sets how much damage the watermark can survive and how many characters fit: stronger correction survives compression and cropping better but fits fewer characters. Defaults to `BCH_4`.
`model_type`	string	optional	Watermark profile that trades robustness against image quality. Defaults to `B`.
`strength`	number	optional	Watermark strength, defaults to `1.0`. Higher survives compression and reposting better but is more likely to be visible; lower is more discreet but less robust.

Response

200 / OK

Embedded successfully; returns the watermarked image (Base64).

JSON

{
  // Base64-encoded watermarked image.
  "image_base64": "string",
  // Image file name (present only if provided on input).
  "image_name": "string",
  // Output image format.
  "format": "png",
  // The marker actually embedded, matching the request.
  "payload": "a1B2c3D",
  // Maximum marker length embeddable under the current settings.
  "capacity_chars": 7,
  // Embed time, in milliseconds.
  "embed_ms": 118.4
}

400 / Bad Request

Bad request, e.g. missing image source or missing payload.

JSON

{
  "code": "INVALID_PARAMETER",
  "message": "an image source is required"
}

413 /

Image too large, exceeding the server limit.

JSON

{
  "code": "FILE_TOO_LARGE",
  "message": "the uploaded image is too large"
}

503 / Service Unavailable

The watermark service is temporarily unavailable.

JSON

{
  "code": "SERVICE_TEMPORARILY_UNAVAILABLE",
  "message": "the watermark service is temporarily unavailable"
}

Quick start

Pick your language to see usage examples

Auth mode:

cURL command

curl -X POST 'https://uapis.cn/api/v1/watermark/embed' \
  -H 'Authorization: Bearer YOUR_API_KEY' \
  -F 'payload=a1B2c3D'

Frequently asked questions

Does it hurt image quality?

Hardly at all. The watermark is written invisibly; you won't notice a difference during normal sharing and viewing.

How much can I embed?

Check capacity_chars in the response — that's the maximum length under the current settings. Store a short code only and keep the full data in your own database.

Can it still be read after forwarding through WeChat or QQ?

The defaults are tuned for the recompression common on social platforms, so normal (compressed) sends usually still read back reliably.

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