Refactor PNG generation

Gemfile

@@ -33,7 +33,6 @@ gem 'rack-rewrite',         '~> 1.5.0'
 gem 'oj',                   '~> 2.11'
 gem 'oj_mimic_json',        '~> 1.0'
 gem 'foreigner',            '~> 1.7'
-gem 'chunky_png',           '~> 1.3'
 
 group :development do
   gem 'quiet_assets',   '~> 1.0.1'
@@ -65,6 +64,7 @@ group :test do
   gem 'shoulda-matchers'
   gem 'coveralls',          require: false
   gem 'rspec-activemodel-mocks'
+  gem 'chunky_png'
 end
 
 group :production do

Gemfile.lock

@@ -350,7 +350,7 @@ DEPENDENCIES
   capistrano-ext (~> 1.2)
   capybara (~> 2.4.1)
   carrierwave (~> 0.8.0)
-  chunky_png (~> 1.3)
+  chunky_png
   coffee-rails (~> 4.0.1)
   coveralls
   dalli (~> 2.6.2)

app/services/asciicast_image_updater.rb

@@ -1,25 +1,28 @@
 class AsciicastImageUpdater
+  PIXEL_DENSITY = 2
 
-  attr_reader :png_generator
+  attr_reader :rasterizer, :image_inspector
 
-  def initialize(png_generator = PngGenerator.new)
-    @png_generator = png_generator
+  def initialize(rasterizer = Rasterizer.new, image_inspector = ImageInspector.new)
+    @rasterizer = rasterizer
+    @image_inspector = image_inspector
   end
 
   def update(asciicast, page_path)
     Dir.mktmpdir do |dir|
-      png_path = "#{dir}/#{asciicast.image_filename}"
+      image_path = "#{dir}/#{asciicast.image_filename}"
 
-      png_generator.generate(page_path, png_path)
+      rasterizer.generate_image(page_path, image_path, 'png', '.asciinema-player', PIXEL_DENSITY)
 
-      File.open(png_path) do |f|
+      File.open(image_path) do |f|
         asciicast.image = f
       end
 
-      image = ChunkyPNG::Image.from_file(png_path)
-      # image has double density so "display" size is half the actual one
-      asciicast.image_width = image.width / 2
-      asciicast.image_height = image.height / 2
+      width, height = image_inspector.get_size(image_path)
+
+      # "display" size is 1/PIXEL_DENSITY of the actual one
+      asciicast.image_width = width / PIXEL_DENSITY
+      asciicast.image_height = height / PIXEL_DENSITY
 
       asciicast.save!
     end

app/services/image_inspector.rb

@@ -0,0 +1,15 @@
+require 'open3'
+
+class ImageInspector
+
+  def get_size(image_path)
+    o, e, t = Open3.capture3(%(identify -format "%[fx:w]x%[fx:h]" #{image_path}))
+
+    if t.exitstatus != 0
+      raise RuntimeError, "Couldn't inspect image #{image_path}:\n#{o}\n#{e}"
+    end
+
+    o.split('x').map(&:to_i)
+  end
+
+end

app/services/png_generator.rb

@@ -1,15 +0,0 @@
-require 'open3'
-
-class PngGenerator
-
-  BINARY_PATH = (Rails.root + "bin" + "asciicast2png").to_s
-
-  def generate(page_path, png_path)
-    o, e, t = Open3.capture3("#{BINARY_PATH} #{page_path} #{png_path}")
-
-    if t.exitstatus != 0
-      raise RuntimeError, "Couldn't generate PNG for #{page_path}:\n#{o}\n#{e}"
-    end
-  end
-
-end

app/services/rasterizer.rb

@@ -0,0 +1,15 @@
+require 'open3'
+
+class Rasterizer
+
+  BINARY_PATH = (Rails.root + "bin" + "rasterize").to_s
+
+  def generate_image(page_path, image_path, format, selector, scale)
+    o, e, t = Open3.capture3("#{BINARY_PATH} #{page_path} #{image_path} #{format} #{selector} #{scale}")
+
+    if t.exitstatus != 0
+      raise RuntimeError, "Couldn't generate image from #{page_path}:\n#{o}\n#{e}"
+    end
+  end
+
+end

bin/rasterize

@@ -2,17 +2,26 @@
 
 var system = require('system');
 
-if (system.args.length < 3) {
-  console.log("usage: " + system.args[0] + " <url> <filename.png>");
+if (system.args.length < 6) {
+  console.log("usage: " + system.args[0] + " <url> <filename> <format> <selector> <scale>");
+  console.log("   ex: " + system.args[0] + " page.html page.png png 'body > div' 2");
   phantom.exit(1);
 }
 
 var url = system.args[1];
 var filename = system.args[2];
+var format = system.args[3];
+var selector = system.args[4];
+var scale = parseInt(system.args[5], 10);
+
 var page = require('webpage').create();
 
 page.viewportSize = { width: 9999, height: 9999 };
-page.zoomFactor = 2;
+page.zoomFactor = scale;
+
+page.onConsoleMessage = function(msg) {
+  console.log('console.log: ' + msg);
+};
 
 page.onError = function(msg, trace) {
   console.log('Script error: ' + msg);
@@ -31,7 +40,7 @@ page.open(url, function(status) {
     phantom.exit(1);
   }
 
-  var size = page.evaluate(function() {
+  var rect = page.evaluate(function(selector) {
     // Alternative to zoomFactor:
     //
     // /* scale the whole body */
@@ -42,18 +51,27 @@ page.open(url, function(status) {
     //
     // It has small issue with letter spacing though.
 
-    var term = $('.asciinema-player');
-    return [term.width(), term.height()];
-  });
+    var elements = document.querySelectorAll(selector);
 
-  if (!size[0]) {
-    console.log("Couldn't get dimensions of the player");
+    if (elements.length > 0) {
+      return elements[0].getBoundingClientRect();
+    }
+  }, selector);
+
+  if (!rect) {
+    console.log("Couldn't get geometry of requested DOM element");
     phantom.exit(1);
     return;
   }
 
-  page.clipRect = { left: 0, top: 0, width: size[0] * 2, height: size[1] * 2 };
-  page.render(filename, { format: 'png' });
+  page.clipRect = {
+    left: rect.left * scale,
+    top: rect.top * scale,
+    width: rect.width * scale,
+    height: rect.height * scale
+  };
+
+  page.render(filename, { format: format });
   phantom.exit(0);
 });
 

spec/services/image_inspector.rb

@@ -0,0 +1,22 @@
+require 'rails_helper'
+
+describe ImageInspector do
+
+  let(:image_inspector) { ImageInspector.new }
+
+  describe '#get_size' do
+    it 'returns width and height of the image' do
+      w, h = image_inspector.get_size("#{Rails.root}/spec/fixtures/new-logo-bars.png")
+
+      expect(w).to eq(154)
+      expect(h).to eq(33)
+    end
+
+    context 'when file is not an image' do
+      it 'raises error' do
+        expect { image_inspector.get_size("#{Rails.root}/spec/fixtures/snapshot.json") }.to raise_error(RuntimeError)
+      end
+    end
+  end
+
+end