Using Headless Chrome to Automate Image Generation on Heroku

Jared Fraser — Sat, 17 Oct 2020 06:32:09 +0000

I automate some posting some daily shop rotations in popular games on my site xstats.gg to twitter - see an example

Building the image as a webpage first allows me to iterate quickly and keep the styles in parity with the rest of the site.

I use Chrome to load up the page and take a screenshot, and a seperate process tweets the image and posts to other social media.

Buildpacks

1. heroku/ruby
2. https://github.com/heroku/heroku-buildpack-chromedriver
3. https://github.com/heroku/heroku-buildpack-google-chrome

Code

class Screenshot
  def capture
    setup
    take_photo
  end

  def setup
    chrome_shim = ENV.fetch("GOOGLE_CHROME_SHIM", nil)
    chrome_bin = ENV.fetch("GOOGLE_CHROME_BIN", nil)

    Selenium::WebDriver::Chrome.path = chrome_bin if chrome_bin
    options = Selenium::WebDriver::Chrome::Options.new
    options.add_argument('--headless')
    options.add_argument('--hide-scrollbars')
    options.add_argument('--no-sandbox')
    options.add_argument('--disable-gpu')
    options.add_argument('--disable-dev-shm-usage')
    options.binary = chrome_shim if chrome_shim
    @driver = Selenium::WebDriver.for :chrome, options: options
  end

  def tmp_file_path
    Rails.root.join("tmp", "screenshot-#{name}.png")
  end

  def take_photo
    driver.navigate.to("https://xstats.gg#{url}")
    max_height = driver.execute_script("return Math.max(document.body.scrollHeight, document.documentElement.scrollHeight, document.body.offsetHeight, document.documentElement.offsetHeight, document.body.clientHeight, document.documentElement.clientHeight);")
    driver.manage.window.resize_to(1000, max_height)
    driver.save_screenshot tmp_file_path
    driver.close
  end
end

ML classification on short strings in Ruby using Smalltext

Jared Fraser — Wed, 09 Jan 2019 04:49:21 +0000

I have a ruby application that pulls in various blog and forum posts from the internet (like a game dev tracker) and needed a way to classify them. Some simple rules got me 75% of the way there - does it include the word "patch" or "patch notes"? then it's likely a patch notes or announcement post - but that wasn't completely reliable. For example, a post reporting a bug on a patch might be worded as "Empty inventory because of Patch 9.0.0.2076", or a post might be announcing a patch deployment but not include any notes.

Recently I found the gem smalltext which has solved most of my problems. It classifies quickly and is pretty simple to train.

I built a training script that hardcodes training data into categories, then trains and saves a model.

lib/train_classifier.rb

require 'smalltext'

data = {
  patch_notes: [
    "PC Client Update - 12/7/2018",
    "v6.31 Patch Notes",
  ],

  news: [
    "$1,000,000 Winter Royale + Tournament Updates",
    "Pop-Up Cups Update 12/5/2018",
  ],
}


s = Smalltext::Classifier.new
data.each do |classification, titles|
  titles.each do |title|
    s.add_item(classification.to_s, title)
  end
end

s.train
s.save_model("classifications.model")

I update this training script with definite examples and incorrectly classified posts as time goes on to improve the model.

app/services/classifier.rb

class Classifier
  def self.classify(text, threshold = 0.99)

    # Load the classifier and the trained model
    @classifier ||
      ((@classifier = Smalltext::Classifier.new) && @classifier.load_model('classifications.model'))

    classified = @classifier.classify(text).to_h
    # { "patch_notes" => 0.9998900049414214 }

    # Return the first category that meets the threshold
    result = classified.detect {|k,v| v >= threshold }
    result.present? ? result.first : nil
  end
end

This class gives my application an entry point to the classifier. I only care about reasonably certain classifications so I built this to only output a classification if the result is above a certain threshold. In my application, I either get a category or nil, which makes it easier for me to handle.