Image watermark

Image watermark is an API that overlays text or your logo on a photo or image. The sibling of PDF watermark, for when what needs marking is a loose image, not a document.

How it works

You send an image and, either text or your logo (another image), and get back the first one with the mark overlaid. By default it comes out diagonal, centered and semi-transparent.

Only one at a time: text OR logo, never both in the same call.

All you need

Your API key. Create it in your dashboard with "+ Create key". It's shown only once, so copy and save it.
In your automation platform, an "HTTP Request" step (n8n, Make, Zapier, Pipedream… all have one).

Text watermark: how to use it in n8n

You send your image as-is (binary) and the text as a parameter. In the HTTP Request node:

Method: POST
URL: https://api.cofferdock.com/image-watermark
Send Query Parameters: on → add text = © My Company (and whatever else: opacity, position… see the table).
Send Headers: on → add x-api-key = your key.
Send Body: on → choose to send a binary file (in n8n: "n8n Binary File").
In Options → Response → Response Format: choose File

Watermark with your logo

To use a logo instead of text, you need to send two images at once, so this only works with a JSON body:

{ "file": "<your image in base64>", "image": "<your logo in base64>" }

Options

Option	Default	What it does
`text`	-	The watermark text (max 200 characters). Use this OR `image`.
`image`	-	Your logo in base64. JSON body only.
`position`	`center`	`center`, `top-left`, `top-right`, `bottom-left`, `bottom-right`.
`opacity`	`0.3`	0.05 (nearly invisible) to 1 (solid).
`rotation`	`45`	Degrees.

API overview

Endpoint: POST https://api.cofferdock.com/image-watermark
Auth: header x-api-key: YOUR_KEY.
Input: text → raw image (with text as a query param) or JSON { file, text, ... }. Logo → JSON ONLY, { file, image, ... }.
Engine: sharp (libvips) + an image-sized SVG overlay. No browser, no external binaries.
Limits: 30 requests/min per IP. 1 watermark = 1 credit.

Options

Option	Default	Description
`text`	-	Max 200 characters. Exactly one of `text`/`image`.
`image`	-	Base64 of an image. JSON mode only.
`position`	`center`	Center or a corner.
`opacity`	`0.3`	0.05–1.
`rotation`	`45`	Degrees, any value.
`font_size`	~6% of width	8–400 px. Only applies to `text`.
`color`	`#808080`	Hex. Only applies to `text`.
`scale`	`0.3`	0.05–1: fraction of the width the logo takes up. Only applies to `image`.
`format`	same as input	`jpeg`, `png`, `webp` or `avif`.

Examples

curl:

curl -X POST "https://api.cofferdock.com/image-watermark?text=CONFIDENTIAL" \
  -H "x-api-key: YOUR_KEY" \
  -H "Content-Type: image/png" \
  --data-binary @photo.png \
  --output watermarked.png

Response

{ "success": true, "image": "iVBORw0KGgo...", "mime_type": "image/png",
    "meta": { "type": "text", "format": "png", "width": 1200, "height": 800,
    "size_bytes": 84213, "used": 12, "remaining": 488 } }

What you get back

By default: with the raw image it returns the image; with JSON it returns base64. Add output=image to force the binary, or output=url for a temporary link (valid 15 minutes).