Wrapped gist up in an application

.gitignore

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+*.gem
+.rvmrc
+*.tar.gz
+rdoc
+Gemfile.lock
+html
+pkg

Gemfile

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+source :rubygems
+gemspec

Rakefile

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+require 'rubygems'
+require 'rubygems/package_task'
+require 'rdoc/task'
+
+RDoc::Task.new do |rd|
+  rd.main = "README.rdoc"
+  rd.rdoc_files.include("README.rdoc","lib/**/*.rb","bin/**/*")
+  rd.title = 'Your application title'
+end
+
+spec = eval(File.read('web_regression.gemspec'))
+
+Gem::PackageTask.new(spec) do |pkg|
+end
+
+require 'rake/testtask'
+Rake::TestTask.new do |t|
+  t.libs << "test"
+  t.test_files = FileList['test/**/*_test.rb']
+end
+
+task :default => :test

bin/web-regression

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+#!/usr/bin/env ruby
+
+unless File.respond_to? :realpath
+  class File #:nodoc:
+    def self.realpath path
+      return realpath(File.readlink(path)) if symlink?(path)
+      path
+    end
+  end
+end
+$: << File.expand_path(File.dirname(File.realpath(__FILE__)) + '/../lib')
+require 'web_regression'
+
+WebRegression::Cli.execute($PROGRAM_NAME,ARGV)

lib/web_regression.rb

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+module WebRegression
+end
+
+require 'web_regression/version'
+require 'web_regression/application'
+require 'web_regression/cli'
+require 'web_regression/comparator'
+

lib/web_regression/application.rb

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+require 'uri'
+
+class WebRegression::Application
+  def initialize(options)
+    @options = options
+  end
+
+  def start
+    reference_file = @options.reference_file
+    uri = URI(@options.url)
+    return WebRegression::Comparator.new(reference_file,"#{uri.scheme}://#{uri.host}:#{uri.port}",uri.path,@options).compare
+  end
+end

lib/web_regression/cli.rb

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+require 'optparse'
+require 'ostruct'
+
+module WebRegression
+  class Cli
+    def self.parse_options(program,args)
+      options = OpenStruct.new
+      options.fastfail = false
+      options.nodiff   = false
+      options.opendiff = false
+      options.reference_file = "/tmp/reference.png"
+
+      opts = OptionParser.new do |opts|
+        executable = File.basename(program)
+        opts.banner = "Usage: #{executable} [options] URL"
+        opts.separator ""
+
+        opts.on_tail("-h", "--help", "Show this message") do
+          puts opts
+          exit
+        end
+
+        opts.on("-r","--reference_png PNG_FILE","Png file to compare against") do |f|
+          options.reference_file = f
+        end
+
+        opts.on("-f", "--fastfail","Fail as soon as a difference detected. Implies -n") do 
+          options.fastfail = true
+        end
+
+        opts.on("-n", "--nodiff","Don't create a diff png") do 
+          options.nodiff = true
+        end
+
+        opts.on("-o", "--opendiff","Open the diff file") do 
+          options.opendiff = true
+        end
+
+        opts.on_tail("--version", "Show version") do
+           puts WebRegression::VERSION
+           exit
+        end
+      end
+      opts.parse!(args)
+      if ARGV.length != 1
+        puts opts
+        exit
+      end
+      options.url = ARGV[0]
+      options
+    end
+
+    def self.execute(program,args)
+      options = parse_options(program,args)
+      app = WebRegression::Application.new(options)
+      exit app.start
+    end
+  end
+end

lib/web_regression/comparator.rb

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+require 'capybara'
+require 'capybara/dsl'
+require 'capybara/poltergeist'
+require 'chunky_png'
+require 'tempfile'  
+
+Capybara.run_server = false
+Capybara.default_driver = :poltergeist
+Capybara.javascript_driver = :poltergeist
+
+class WebRegression::Comparator < Struct.new(:reference_file,:host,:path,:options)
+  include Capybara::DSL
+
+  SUCCESS, FAILURE = 0,1
+
+  def take_screenshot(name)
+    Capybara.app_host = self.host
+    visit(self.path);
+    page.driver.render(name,:full => true)
+  end
+
+  def ensure_reference_image
+    unless File.exists?(self.reference_file)
+      $stderr.puts "Creating a reference screenshot at #{self.reference_file}"
+      take_screenshot(self.reference_file)
+    end
+  end
+
+  def screenshot
+    @screenshot ||= begin
+      image_name = '/tmp/ss.png'
+      take_screenshot(image_name)
+      image_name
+    end
+  end
+
+  def checksum_match?(file1, file2)
+    ref_md5 = `md5 #{file1}`
+    new_md5 = `md5 #{file2}`
+    ref_md5 == new_md5
+  end
+
+  def reference_image
+    @reference_image ||= ChunkyPNG::Image.from_file(self.reference_file)
+  end
+
+  def new_image
+    @new_image ||= ChunkyPNG::Image.from_file(screenshot)
+  end
+
+  def highlight_diffs(new_image,diff)
+     x, y = diff.map{ |xy| xy[0] }, diff.map{ |xy| xy[1] }
+
+     new_image.rect(x.min, y.min, x.max, y.max, ChunkyPNG::Color.rgb(255,0,0))
+     diff_path = '/tmp/diff.png'
+     new_image.save(diff_path)
+
+     if options.opendiff
+       `open #{diff_path}`
+     end
+  end
+
+  def compare
+     ensure_reference_image
+
+     return SUCCESS if checksum_match?(self.reference_file,screenshot)
+
+     diff = []
+
+     reference_image.height.times do |y|
+       reference_image.row(y).each_with_index do |pixel, x|
+         unless pixel == new_image[x,y]
+          return FAILURE if options.fastfail
+          diff << [x,y] 
+         end
+       end
+     end
+
+     return SUCCESS if diff.length == 0
+
+     unless options.nodiff
+       highlight_diffs(new_image,diff)
+     end
+
+     return FAILURE
+  end
+
+end

lib/web_regression/version.rb

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+module WebRegression
+  VERSION = '0.9'
+end

test/null_test.rb

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+require 'test/unit'
+
+class NullTest < Test::Unit::TestCase
+
+  def setup
+  end
+
+  def teardown
+  end
+
+  def test_the_truth
+    assert true
+  end
+end

web_regression.gemspec

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+require File.join([File.dirname(__FILE__),'lib','web_regression','version.rb'])
+spec = Gem::Specification.new do |s| 
+  s.name = 'web_regression'
+  s.version = WebRegression::VERSION
+  s.author = 'Ben Griffiths'
+  s.email = 'bengriffiths@gmail.com'
+  s.homepage = 'http://techbelly.com'
+  s.platform = Gem::Platform::RUBY
+  s.summary = 'Simple guard-friendly utility for diffing web screenshots to make css refactoring easier'
+  s.files = %w(
+bin/web-regression
+  )
+  s.require_paths << 'lib'
+  s.has_rdoc = false
+  s.bindir = 'bin'
+  s.executables << 'web-regression'
+
+  s.add_dependency('chunky_png')
+  s.add_dependency('poltergeist')
+
+  s.add_development_dependency('rake')
+  s.add_development_dependency('rdoc')
+end