Extract screenshots from recorded profile in Google Chrome Dev tools

extract_screenshots.rb

#!/usr/bin/env ruby

require 'optparse'
require 'json'
require 'base64'
require 'pathname'

module Screenshot
  class Snapshot
    attr_reader :name, :ts, :blob, :format

    def initialize(name, ts, blob)
      @name = name
      @ts = ts
      @blob = blob
      @format = 'jpeg'
    end

    def save!(directory)
      filename = Pathname.new(directory).join("#{name}-#{ts}.#{format}")
      File.write(filename, Base64.decode64(blob))
    end
  end

  def self.parse(frame)
    Snapshot.new(frame['name'], frame['ts'], frame['args']['snapshot'])
  end
end

options = {}
opt_parser = OptionParser.new do |opts|
  opts.banner = 'Usage: extract_screenshots [options]'

  options[:file] = nil
  opts.on('-f', '--file FILE', String, 'File with recorder profiling data') do |f|
    options[:file] = f
  end

  opts.on('-h', '--help', 'Show help') do |h|
    options[:help] = h
    puts opt_parser
    exit
  end
end

begin
  opt_parser.parse!(ARGV)
  file = options.fetch(:file)

  # might take a while if file is very big
  frames = JSON.parse(File.read(file)).select { |r| r['name'] == 'Screenshot' }
  frames.each do |frame|
    snapshot = Screenshot.parse(frame)
    snapshot.save!(Dir.pwd) # save all files to current directory
  end
rescue OptionParser::InvalidOption, OptionParser::MissingArgument
  puts $!.to_s
  puts opt_parser
  exit
end