ShareMeow is a Ruby microservice (ooh ahh) for creating super shareable, tweetable, facebook-able images from your content 😻. You define a template (using HTML/CSS), pass it some parameters, and it will generate an image to you.

It's what we use at Product Hunt for making beautiful tweets like this:

• Supports Emoji 💯😻✨
• Custom fonts
• Cachable images (throw cloudflare infront of it & you're good to go)
• signed URLs via hmac digest

For a quick introduction to how to use ShareMeow, take a look at this excellent screencast by GoRails.

This generates and returns a jpg.

Required params are determined by the image template you're using.

If you're using Ruby, you can use the ShareMeow Ruby Client for generating URLs easily.

If you'd rather not use the client. Here is an example of how to generate the URL in Ruby.

require 'base64'
require 'json'
require 'openssl'

json_params = { template: 'HelloWorld', message: 'Hello' }.to_json

encoded_params = Base64.urlsafe_encode64(json_params)
hmac = OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha1'), 'your_secret_key', encoded_params)
hmac_digest = Base64.urlsafe_encode64([hmac].pack('H*'))

image_url = "https://your-share-meow.herokuapp.com/v1/#{ encoded_params }/#{ hmac_digest }/image.jpg"


# => "https://your-share-meow.herokuapp.com/v1/eyJ0ZW1wbGF0ZSI6IkhlbGxvV29ybGQiLCJtZXNzYWdlIjoiSGVsbG8ifQ==/-lgitNQmEs9NaiWyOCHeV137D80=/image.jpg"

ShareMeow uses URLs signed with an HMAC signature to ensure that only people with a secret key are able to generate URLs with your service.

It works like this:

Convert your parameters to JSON. Then Base64 URL Safe encode them. There are libraries available to do this in all major languages.

# Ruby
params = { template: 'HelloWorld', message: 'Hello, World' }
json_params = params.to_json

encoded_params = Base64.urlsafe_encode64(json_params)

Then create the HMAC signature from the encoded params and your secret key. Finish by packing and base64 encoding the signature (we do this to keep the URL shorter)

hmac_signature = OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha1'), 'your_secret_key', encoded_params)
encoded_hmac = Base64.urlsafe_encode64([hmac_signature].pack('H*'))

When ShareMeow gets your request, it will recreate the HMAC signature using the encoded params/secret key. If it matches the signature you provided, it will generate the image. ⭐

Take a look here for example templates: https://github.com/producthunt/ShareMeow/tree/master/app/image_templates.

Here is example css using a font from Google Fonts.

@font-face {
  font-family: 'Roboto';
  font-style: normal;
  font-weight: 400;
  src: local('Roboto Regular'), local('Roboto-Regular'), url(https://themes.googleusercontent.com/static/fonts/roboto/v10/2UX7WLTfW3W8TclTUvlFyQ.woff) format('woff');
}

If you'd like to render emoji, you can use the EmojiHelper in your templates. It converts both unicode emoji and GitHub/Slack (:smile:) style emoji to images. Can do this by overriding render_options.

# images_templates/your_template.rb
require 'app/emoji_helper'

module ImageTemplates
  class YourTemplate < Base
    def render_options
      @options[:content] = EmojiHelper.emojify(@options[:content])
      super
    end
  end
end

After checking out the repo, run bundle install to install dependencies. Then, run rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Start the server: $ puma

Want to make this better? Great! 😄

Bug reports and pull requests are welcome on GitHub at https://github.com/producthunt/ShareMeow. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

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