---
title: "Adding an image watermark"
description: "Discover how to effortlessly add image watermarks to PDFs using Ruby and the Net::HTTP library. Our guide shows you how to add images on top of your PDF to protect your document easily. This is easily done with a simple request to PDFShift's API."
language: 'Ruby'
library: 'Net::HTTP'
property: 'watermark'
output: 'pdf'
related: ['protecting-the-generated-pdf', 'adding-a-text-watermark']
default: true
---

In this guide, we'll walk you through the process of adding text watermarks to your PDF files, using PDFShift's API.

Adding a watermark to your PDF can be done by adding the `watermark` object to your query.
The advantage of providing an image is that you can add a visual stamp on top of each of your pages that are generated through PDFShift.

```ruby
require 'net/http'
require 'uri'
require 'json'

# You can get an API key at https://pdfshift.io
api_key = 'sk_xxxxxxxxxxxx'

params = {
    'source' => 'https://www.example.com',
    'watermark' => {
        'image' => 'https://placekitten.com/200/300',
        'offset_x' => 'center',
        'offset_top' => 'top'
    }
}

url = URI("https://api.pdfshift.io/v3/convert/pdf")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request['Content-Type'] = 'application/json'
request['X-API-Key'] = api_key
request.body = params.to_json

# Send the request and handle the response
response = http.request(request)

# write response to a file nammed "result.pdf"
File.open('result.pdf', 'wb') { |f| f.write(response.body) }

# Print a success message
puts 'The PDF document was generated and saved to result.pdf'
```

The "image" parameter for the watermark can be used in two different values:

 * URL : A full URL to an image that will be used as the watermark.
 * Base64 : A base64 encoded image that will be used as the watermark.

Note that you can also rotate the image by passing the `rotate` parameter as a degree (or negative degree)

You can also customize the position of the text watermark by applying the following properties:

 * `offset_x`: The horizontal position of the text. Can be 'left', 'center', 'right', or a specific value in pixels. Defaults to 'center'.
 * `offset_y`: The vertical position of the text. Can be 'top', 'middle', 'bottom', or a specific value in pixels. Defaults to 'center'.

For the offset positions, we accept a value in integer which will be translated to pixels, but you can also pass a unit such as 'px', 'in', 'cm', 'mm', 'pt'.

For example:

```json
params = {
    "source": "https://www.example.com",
    "watermark": {
        "text": "PROTECTED DOCUMENT",
        "offset_x": "5cm",
        "offset_top": "15mm"
    }
}
```