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Including images with Liquid

A while ago I covered on Using Jekyll, Lightbox, and GitHub pages how to use includes in Jekyll/Liquid to simplify the process of adding images to your posts.

The process is pretty simple, but you need two different files (and syntaxes) for essentially the same thing: showing an image. This probably makes sense from a technical point of view, but it's just cumbersome to use.

I also realised I had no way of displaying images from external sources (i.e., from an URL), so I decided to revamp my includes and merge them into just one that can:

  • Handle URLs and local images easily.
  • Use Lightbox if needed.

Implementation

I didn't want to use different variables to handle local images and URLs, so my idea was to use pattern matching in the src variable to check if it is an URL, like so: 

{% unless include.src contains 'http' %}
  <img width="{{ include.width }}" src="{{ '/assets/img/' | prepend: site.baseurl | replace: 'http://', 'https://' }}{{ include.src }}" alt="{{ include.title }}"/>
{% else %}
  <img width="{{ include.width }}" src="{{ include.src }}" alt="{{ include.title }}"/>
{% endunless %}

I'm using the unless control flow tag instead of if, as I will be using local images more often than not. As a result, the build process should be faster (negligibly so, but it's always a good practice to think about the evaluation process of your code).

For handling Lightbox, I'm doing pretty much the same, so I'll spare the explanation. At the end, I ended up with a pretty straightforward implementation: 

{% unless include.lightbox == "true" %}
  {% unless include.src contains 'http' %}
  <img width="{{ include.width }}" src="{{ '/assets/img/' | prepend: site.baseurl | replace: 'http://', 'https://' }}{{ include.src }}" alt="{{ include.title }}"/>
  {% else %}
  <img width="{{ include.width }}" src="{{ include.src }}" alt="{{ include.title }}"/>
  {% endunless %}
{% else %}
  {% unless include.src contains 'http' %}
  <a href="{{ '/assets/img/' | prepend: site.baseurl | replace: 'http://', 'https://' }}{{ include.src }}" data-lightbox="{{ include.data }}" data-title="{{ include.title }}"><img width="{{ include.width }}" src="{{ '/assets/img/' | prepend: site.baseurl | replace: 'http://', 'https://' }}{{ include.src }}" alt="{{ include.title }}"/></a>
  {% else %}
  <a href="{{ include.src }}" data-lightbox="{{ include.data }}" data-title="{{ include.title }}"><img width="{{ include.width }}" src="{{ include.src }}" alt="{{ include.title }}"/></a>
  {% endunless %}
{% endunless %}

Usage

In my Markdown templates I'm using the snippet below: 

{% include image.html lightbox="false" src="file.jpg" data="group" title="Image title" width="100%" %}

By default, when using standard images, the lightbox and data variables are not needed; the former doesn't really need to be false (it just needs to be not true, which is different), and the later is only evaluated when using Lightbox.

The width variable is also optional. By default, my CSS code forces the max-width to be 100%, so big images will be shrank down to the text width, and smaller images will be displayed at real size. Sometimes, however, I want to force big images to be 50% of the text width (or any other value).

That being said, I prefer to include all these variables in my template to ease the use of the include, as it's always easier to remove parts of the snippet than to remember the entire syntax.