Let's start with sample of what this gem can do (below are the images of generated previews):

Demo: https://www.youtube.com/watch?v=Lso-B_fayhw

If you need to generate complex images, previews, charts or basically represent any HTML snippet - this gem could help.

It's using a Chrome(headless) to convert any HTML to PNG.

If you want to try, you just need a 5 min to see how it works. Gem is comming with an examples which you can modify and use in your real app.

• add this gem to Gemfile - gem "omg_image"
• make sure you have chrome installed (google-chrome --version)
• execute rails g omg in app
• execute rake db:migrate
• edit sample template app/omg/simple.html.erb
• open any view, for example you have app/views/home/index.html.erb and put:

  <%= image_tag OmgImage::Processor.new('entity', key: 'xxx', title: "OMG,<br/>this looks interesting!", tags: ['This', 'is', 'a', 'sample'], description: "Change me please", size: '600,300').cached_or_new %>
  <br/>
  <%= image_tag OmgImage::Processor.new('entity', title: "OMG,<br/>this looks interesting!", description: "Small version", size: '400,200').cached_or_new(regenerate: true) %>
  <br/>
  <%= image_tag OmgImage::Processor.new('square', title: "Real-time generation", size: '200,200').cached_or_new %>

• refresh page and see images
• edit/create new previews and use them in any place of your app.

Also, for example you can do it on generate images directly in the models:

class Post < ApplicationRecord
  has_one_attached :preview
  # just an example
  def Post.create_new_preview
    processor = ::OmgImage::Processor.new('entity', title: "OMG,<br/>this is created from model", description: "Small version", size: '400,200')
    processor.with_screenshot do |screenshot|
      post = Post.new
      post.preview.attach(io: File.open(screenshot.path), filename: "image.png", content_type: "image/png")
      post.save!
    end
  end
end

To create a new template - basically create a new file in app/omg/<name>.html.erb. Put any HTML/CSS into it. And use as described above.

• Rails App 5+ and Active Storage
• Google chrome (headless)

Add this line to your application's Gemfile:

gem 'omg_image'

And then execute:

$ bundle

• you can generate images with any complexity (you just need to know html/css)
• store cached versions of preview by key and you can obtain them by OmgImage::Image.find_by(key: key)
• generate images in background jobs or console applications
• caching for previews by key
• ability to refresh preview by key

• .cached_or_new(regenerate: true) pass this option with true value if you want to regenerate image

• sudo apt install gdebi-core
• wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
• sudo gdebi google-chrome-stable_current_amd64.deb
• verify chrome is installed google-chrome --version

• https://linuxize.com/post/how-to-install-google-chrome-web-browser-on-ubuntu-18-04/

• if you process too many requests and because of timeouts dead processes may appear. To kill them parents_of_dead_kids=$(ps -ef | grep [d]efunct | awk '{print $3}' | sort | uniq | egrep -v '^1$'); echo "$parents_of_dead_kids" | xargs kill

• ability to configure app (path to chrome for example)
• more samples (with layout)
• wiki pages with documentation and samples
• ability to preview templates directly by URL
• tests/specs
• options to delay rendering (could be useful if use JS libraries or external assets)
• support remote URL's to render (so it would possible to capture screenshots for example)

You are welcome to contribute.

I've noticed that in a past that articles on dev.to site without images when you sending a link in skype or sharing in FB have have nice preview, so I've implemented similar solution :)

The gem is available as open source under the terms of the MIT License.