Adding an image watermark in Ruby with RestClient

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.

require 'rest-client'
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'
    }
}

# Make the POST request
response = RestClient.post("https://api.pdfshift.io/v3/convert/pdf", params.to_json, {
    'Content-Type' => 'application/json',
    'Authorization' => "Basic #{Base64.strict_encode64("api:#{api_key}")}"
})

# Check for successful response
unless response.code == 200
    raise "Request failed with status code #{response.code}: #{response.body}"
end

# 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:

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