Jekyll::Linkpreview

Jekyll plugin to generate link preview by {% linkpreview %} tag. The plugin fetches Open Graph protocol metadata of the designated page to generate preview. The og properties are saved as JSON for caching and it is used when rebuilding the site.

You can pass url directly to the tag,

{% linkpreview "https://github.com/ysk24ok/jekyll-linkpreview" %}

or, can pass a url variable.

{% assign jekyll_linkpreview_page = "https://github.com/ysk24ok/jekyll-linkpreview" %}
{% linkpreview jekyll_linkpreview_page %}

By applying linkpreview.css, the link preview will be like this.

When the page does not have Open Graph protocol metadata, the preview will be like this.

You can override the default templates, see Custom templates.

Installation

See https://jekyllrb.com/docs/plugins/installation/ .

Usage

1. Create _cache directory.

   • This directory must exist under your project root even if you've modified the site source.

2. Embed linkpreview.css into your Website.

3. Use {% linkpreview %} tag.

4. Run jekyll build or jekyll serve.

Custom templates

You can override the default templates used for generating previews, both in case Open Graph protocol metadata exists or does not exist for a given page.

Template for pages where Open Graph protocol metadata exists

1. Place linkpreview.html file inside _includes/ folder of your Jekyll site (_includes/linkpreview.html)

   • The folder is the same one you would store files for use with {% include fragment.html %} tag. Therefore, it must be under the site's source.

2. Use built-in variables to extract data which you would like to render. Available variables are:

   • basic metadata
     • {{ title }} for og:title
     • {{ type }} for og:type
     • {{ image }} for og:image
     • {{ url }} for og:url
   • optional metadata
     • {{ description }} for og:description
     • {{ determiner }} for og:determiner
     • {{ locale }} for og:locale
     • {{ locale_alternate }} for og:locale:alternate
     • {{ site_name }} for og:site_name
     • image
       • {{ image }} for og:image
       • {{ image_secure_url }} for og:image:secure_url
       • {{ image_type }} for og:image:type
       • {{ image_width }} for og:image:width
       • {{ image_height }} for og:image:height
       • {{ image_alt }} for og:image:alt
     • video
       • {{ video }} for og:video
       • {{ video_secure_url }} for og:video:secure_url
       • {{ video_type }} for og:video:type
       • {{ video_width }} for og:video:width
       • {{ video_height }} for og:video:height
     • audio
       • {{ audio }} for og:audio
       • {{ audio_secure_url }} for og:audio:secure_url
       • {{ audio_type }} for og:audio:type
   • non og metadata
     • {{ domain }}

Template for pages where Open Graph protocol metadata does not exist

1. Place linkpreview_nog.html file inside _includes/ folder of your Jekyll site (_includes/linkpreview_nog.html)

   • The folder is the same one you would store files for use with {% include fragment.html %} tag. Therefore, it must be under the site's source.

2. Use built-in variables to extract data which you would like to render. Available variables are:

   • {{ title }}
   • {{ url }}
   • {{ description }}
   • {{ domain }}

Development

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

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Test with Jekyll site

First, build a Docker image and run a container.

$ docker build --no-cache -t jekyll_linkpreview_dev .
$ docker run --rm -it -w /jekyll-linkpreview -p 4000:4000 jekyll_linkpreview_dev /bin/bash

Create a new Jekyll site and move into the new directory.

# bundle exec jekyll new testsite && cd testsite

Add this line to :jekyll_plugins group of Gemfile.

gem "jekyll-linkpreview", git: "https://github.com/YOUR_ACCOUNT/jekyll-linkpreview", branch: "YOUR_BRANCH"

Install the dependecies to your new site.

# bundle install

Add a tag such as {% linkpreview "https://github.com/ysk24ok/jekyll-linkpreview" %} to index.markdown , then start a Jekyll server.

# bundle exec jekyll serve --host 0.0.0.0

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/ysk24ok/jekyll-linkpreview.

License

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