Save graph generated by rbplotly as PNG by webkit2-gtk

rbplotly-webkit2-gtk-save-image.rb

#!/usr/bin/env ruby

require "rbplotly"
require "webkit2-gtk"

x = [0, 1, 2, 3, 4]
trace0 = { x: x, y: [0, 2, 1, 4, 3], type: :scatter, mode: :lines }
trace1 = { x: x, y: [4, 1, 3, 0, 2], type: :scatter, mode: :'markers+lines' }
data = [trace0, trace1] # data must be an array

layout = { width: 500, height: 500 }

plot = Plotly::Plot.new(data: data, layout: layout)

plot.layout.height = 300 # You can assign plot's attributes.

module Plotly
  class Plot
    def to_html_data
      id = UUIDTools::UUID.random_create.to_s
      html = Offline::HTML.new(id,
                               @data.map(&:to_h),
                               layout: @layout.to_h,
                               config: {},
                               embedded: false)
      html.render
    end
  end
end

main_loop = GLib::MainLoop.new
base_path = "/tmp/x"

view_context = WebKit2Gtk::WebContext.new(ephemeral: true)
view = WebKit2Gtk::WebView.new(context: view_context)
window = Gtk::OffscreenWindow.new
window.add(view)
window.set_default_size(plot.layout.width, plot.layout.height)
window.show_all
view.load_html(plot.to_html_data)
view.signal_connect("load-changed") do |_, load_event|
  case load_event
  when WebKit2Gtk::LoadEvent::FINISHED
    view.get_snapshot(:full_document, :none) do |_, result|
      main_loop.quit
      snapshot_surface = view.get_snapshot_finish(result)
      snapshot_surface.write_to_png("#{base_path}.png")
    end
  end
end
view.signal_connect("load-failed") do |_, _, failed_uri, error|
  main_loop.quit
  message = "failed to load URI: #{failed_uri}: "
  message << "#{error.class}(#{error.code}): #{error.message}"
  puts(message)
  true
end
main_loop.run