screenshot_service.rb

# Small screenshot service that uses headless chrome to take a screenshot
# of your website.
#
class ScreenshotService
  def initialize(url, options: {})
    @url = url
    @options = options
  end
  attr_reader :url, :options

  def self.fetch(url, options: {})
    new(url, options: options).fetch
  end

  def fetch
    session = setup_capybara_session
    session.visit(url)
    resize(session)
    target = random_filename
    session.save_screenshot(target)
    session.quit
    target
  end

  private

  def random_filename
    "/tmp/#{SecureRandom.hex}.png"
  end

  def resize(session)
    return session if width.blank? || height.blank?

    session.current_window.resize_to(width, height)
  end

  def width
    options[:width]
  end

  def height
    options[:height]
  end

  def setup_capybara_session
    Capybara.register_driver :headless_chrome do |app|
      client = Selenium::WebDriver::Remote::Http::Default.new
      client.read_timeout = 120 # instead of the default 60
      options = Selenium::WebDriver::Chrome::Options.new
      options.headless!

      driver_parameters = {
        browser: :chrome,
        http_client: client,
        capabilities: [options]
      }
      Capybara::Selenium::Driver.new(app, **driver_parameters)
    end

    Capybara.default_driver = :headless_chrome
    Capybara.javascript_driver = :headless_chrome
    Capybara::Session.new(:headless_chrome)
  end
end