Example of creating screenshots of your site using Capybara and Selenium, for details: http://blog.appsignal.com/blog/2015/07/21/automated-screenshots-using-capybara.html

screenshots.rake

BROWSER_WIDTH  = 1600
BROWSER_HEIGHT = 1200

Capybara.default_driver = :selenium
include Capybara::DSL

def take_screenshot(path, name, convert_options={})
  # Wait for JS to load data and so on
  sleep 2
  retinafy_screen

  t_file = tmp_file(path, name)
  s_file = screenshot_file(path, name)

    page.save_screenshot(t_file)
    convert(
    t_file,
    s_file,
    convert_options
  )
  optimize(s_file)
end

def retinafy_screen
  # Zoom content to get retina screenshot
  page.driver.execute_script('
     body = document.getElementsByTagName("body")[0];
     body.style["transform-origin"] = "top left";
     body.style["transform"] = "scale(2)";
  ')
end

def tmp_file(path, name)
  Rails.root.join("tmp/#{path || 'root'}_#{name}.png")
end

def screenshot_file(path, name)
  if path
    Rails.root.join("app/assets/images/homepage/screenshots/#{path}/#{name}.png")
  else
    Rails.root.join("app/assets/images/homepage/screenshots/#{name}.png")
  end
end

def url(path)
  "https://appsignal.com#{path}"
end

def crop_arg(width, height, x=0, y=0)
  "#{retina_size(width)}x#{retina_size(height)}+#{retina_size(x)}+#{retina_size(y)}"
end

def retina_size(size)
  size * 2
end

def convert(from_file, to_file, args)
  args_s = args.map do |key, value|
    "-#{key} #{value}"
  end.join(' ')
  `convert #{from_file} #{args_s} #{to_file}`
end

def optimize(file)
  `pngquant --force --output #{file} #{file}`
end

task :homepage do
  visit url('/')
  take_screenshot nil, 'intro', :crop => crop_arg(BROWSER_WIDTH, 650)
end