Open Graph image generation on the fly with Ruby

Prerequisites

At Wannadocs, we're generating Open Graph tags for each article to make it looks as attractive as possible when sharing on social media or messengers.

I didn't want to spend a lot of time on this feature, so I created a 1200x600px image, filled it with the color that a user specified as the primary color in the Knowledge Base theme, and added the title as white text.

It was operating like that for a whole year.

A year later, I began to notice that large companies are moving in this direction. I was excited and wants to know how they do it.

For example:

dev.to

github.com

I did a little investigation. Since the source code of the dev.to is open, I found out that Github and dev.to creating their previews in HTML and send them to a special service that renders previews through Headless Chromium. With the new knowledge, I decided to slightly improve our previews generating to keep it up with the smooth appearance and content.

Since we sell the self-hosted version of Wannadocs, we're not suited to using the third-party service here, so we decided to stay on "libvips" + Ruby.

Let's go!

Installation

First, you need to install all necessary packages on the server and build the "libvips" (Ansible playbook is doing this for me, so I tried to get just shell commands from there):

Here you can find the official manual on how to build it.

Pay attention to these packages:

fonts-open-sans – don't forget about fonts otherwise you will get that:

And libpango1.0-dev – without this library Vips cannot properly write text.

Anatomy

Our previews are very similar to Github:

• Gray text is a knowledge base name, in this case (Demo)
• Big dark text is an article title
• On the right side knowledge base logo
• At the bottom 20px border is the primary color of the knowledge base

Code

I'm also a big fan of jQuery-style DSL with returning of the “self” object from a method and chaining.

With DSL I'm trying to reduce the inconvenience of creating image layout with code and make this snippet more portable from project to project.

In Rails, I created a controller that serves up these images like this:

As a result, we get Open Graph images for all social networks without unnecessary dependencies on third-party services and very fast generation, unfortunately at the cost of the inconvenience of image layout.

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Wannadocs - we make product knowledge bases for your customers, we have:

• Cool editor with support for markdown and embedded elements (YouTube, CodePen, Gist, Figma, Airtable etc.)

• Analytics by the article: views, likes, dislikes

• Built-in full-text search

• Templates and customization

• SSL certificates in two clicks

• Amazing OpenGraph images for your links 😍

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