Add screenshot generator for themes (and screenshots themselves)

lib/screenshot.rb

@@ -0,0 +1,48 @@
+require 'middleman'
+require 'capybara'
+require 'capybara/poltergeist'
+require 'mini_magick'
+
+class Screenshot
+  include Capybara::DSL
+  attr_accessor :theme, :theme_name
+
+  def self.prepare
+    Capybara.register_driver :poltergeist do |app|
+      Capybara::Poltergeist::Driver.new(app, window_size: [1280, 768])
+    end
+    Capybara.default_driver = :poltergeist
+    Capybara.app = ::Middleman::Application.server.inst do
+      set :root, File.expand_path(File.join(File.dirname(__FILE__), '..'))
+      set :environment, :development
+      set :show_exceptions, false
+    end
+  end
+
+  def initialize(theme_name)
+    @theme_name = theme_name
+    @theme = theme_name.parameterize.underscore
+  end
+
+  def generate_theme_image
+    puts "Generating image for theme #{theme_name}"
+    visit '/'
+    within ".theme_#{theme}" do
+      choose 'sidebar_theme_rd'
+    end
+    sleep 1
+    file = Tempfile.new([theme, ".png"])
+    begin
+      page.save_screenshot(file.path, full: true)
+
+      MiniMagick::Tool::Convert.new do |convert|
+        convert << file.path
+        convert.crop '220x220+0+0'
+        convert << "source/images/theme/#{theme}.png"
+      end
+    ensure
+      file.close
+      file.unlink
+    end
+  end
+end