Jekyll Assets

Jekyll Assets is a drop in assetpipeline that usesSprockets to build specificallyfor Jekyll. It utilizes Sprockets,and Jekyll to try and achieve a clean, andextensible assets platform that supports plugins, caching, converting yourassets. It even supports proxying of said assets in a way that does notinterfere with either Sprockets,or Jekyll, or your own source. By default youcan add Jekyll Assets to your Gemfile, as a plugin, and have it act asa drop-in replacement for Jekyll's basic SASS processors, with you onlyhaving to add it to your Gemfile, and updating your <img>, and <link>.

Installing

gem "jekyll-assets", group: :jekyll_plugins
gem "jekyll-assets", git: "https://github.com/envygeeks/jekyll-assets", group: :jekyll_plugins
gem "jekyll-assets", "~> x.x.alpha", group: :jekyll_plugins

System Requirements

• ruby: 2.6+
• sprockets: 4.0+
• uglifier: 4.0
• jekyll: 3.5+

Configuration

The configuration file is the same as Jekyll's, which is _config.yml.Except we use the special key called assets inside of that file.All values listed below are default, you need not copy these into yourconfiguration file unless you plan to change a value. Setting a value makesit explicit, and shared across both production, and development.

# _config.yml
assets:
  source_maps: true
  destination: "/assets"
  compression: false
  gzip: false
  defaults:
    integrity:
      {css,img,js}: false
  caching:
    enabled: true
    path: ".jekyll-cache/assets"
    type: file
  # --
  # Assets you wish to always have compiled.
  #   This can also be combined with raw_precompile which
  #   copies assets without running through the pipeline
  #   making them ultra fast.
  # --
  precompile: []
  raw_precompile: [
    #
  ]
  # --
  # baseurl: whether or not to append site.baseurl
  # destination: the folder you store them in on the CDN.
  # url: the CDN url (fqdn, or w/ identifier).
  # --
  cdn:
    baseurl: false
    destination: false
    url: null
  # --
  # See lib/jekyll/assets/config.rb
  #   for a list of defaults
  # --
  sources:
    - _assets/custom
  plugins:
    css: { autoprefixer: {}}
    img: { optim: {}}

Tag {% asset %}, <img>

{% asset src @magick:double alt='This is my alt' %}
{% asset src @magick:double alt='This is my alt' %}
<img src="src" asset="@magick:double" alt="This is my alt">
<img src="src" alt="This is my alt" asset>

Defaults

We provide several defaults that get set when you run an asset, depending oncontent type, this could be anything from type, all the way to integrity.If there is a default attribute you do not wish to be included, you candisable the attribute with !attribute, and it will be skipped over.

{% asset img.png !integrity %}
{% asset bundle.css !type   %}

Arguments

Our tags will take any number of arguments, arbitrary or not... andconvert them to HTML, and even attach them to your output if theHTML processor you use accepts that kind of data. This appliesto anything but hashes, and arrays. So adding say, a class, orid, is as easy as doing id="val" inside of your tag arguments.

Built In

Responsive Images

<img> usage

Configuration

Each option is in the responsive namespace regardlessof whether it's inside of the tag, or configuration.

Example

{% asset img.png @pic
    srcset:max-width="200"
    srcset:min-width="200"
    srcset:scales=1x
    srcset:scales=2x
    srcset:scales=3x
        %}

<img srcset="
    img-<hash>.png 3x,
    img-<hash>.png 2x,
    img-<hash>.png 1x"
        >

Discovery

When using discovery based responsive images, we will only do responsiveimages if we can find assets that match your scales based on the sourcefile. For example if you do {% asset img.png responsive:discovery responsive:scales=1x responsive:scales=1.5x responsive:scales=2x %} thenwe will expect img.png@1.5x and img.png@2x to exist. For any imagethat doesn't exist it will be skipped, and that scale will not be included!

Automatic

Automatic responsive images/scaling can either upscale, or downscale. Thisis useful if you have a ton of images for blog posts, and you always want toprovide a single most high quality version and then have us downscale those,or if you have an image and wish us to upscale it! The argv1 of {% asset img.png %} is where the source is derived from. Given you give 2x, 1.5xand 1x if you choose to downscale, the source will be assumed to be 2x,and we will downscale to 1.5x and half. If you chose to upscale, the sourcewill be assumed to be 1x, and we will multiply the width by 1.5 and 2

Liquid

We support liquid arguments for tag values (but not tag keys), and we alsosupport Liquid pre-processing (with your Jekyll context) of most files if theyend with .liquid. This will also give you access to our filters as well astheir filters, and Jekyll's filters, and any tags that are globally available.

{% asset '{{ site.bg_img }}' %}
{% asset '{{ site.bg_img }}' proxy:key='{{ value }}' %}
{% asset {{\ site.bg_img\ }} %}

.sass, .scss

body {
  background-image: asset_url("'{{ site.bg_img }}'");
  background-image: asset_url("'{{ site.bg_img }}' proxy:key='{{ value }}'");
  background-image: asset_url("{{\ site.bg_img\ }}");
}

.liquid.ext

.ext.liquid

Supported file types:

• .css
• .sass
• .scss
• .js
• .es6
• .coffee
• .svg

You have full access to your entire global context from any liquid processingwe do. Depending on where you do it, you might or might not also haveaccess to your local (page) context as well. You can also do whatever youlike, and be as dynamic as you like, including full loops, and conditionalLiquid, since we pre-process your text files. On Sprockets 4.x you can use.liquid.ext and .ext.liquid, but because of the way Sprockets 3.x works, wehave opted to only allow the default extension of .ext.liquid when runningon "Old Sprockets" (AKA 3.x.) If you would like Syntax + Liquid you shouldopt to install Sprockets 4.x so you can get the more advanced features.

Importing

**In order to import your Liquid pre-processed assets inside of Liquid or JSyou should use a Sprockets //require=, Sprockets does not integrate thatdeeply into JavaScript and SASS to allow you to @import and pre-process.

.sass, .scss Helpers

We provide two base helpers, asset_path to return the path of an asset,and asset_url which will wrap asset_path into a url() for you,making it easy for you to extract your assets and their paths inside ofSCSS. All other helpers that Sprockets themselves provide will use ourasset_path helper, so you can use them like normal, including with Liquid

body {
  background-image: asset_url("img.png");
}

Proxies, and Other Arguments

Any argument that is supported by our regular tags, is also supported byour .sass/.scss helpers, with a few obvious exceptions (like srcset).This means that you can wrap your assets into magick if you wish, orimageoptim or any other proxy that is able to spit out a path for youto use. The general rule is, that if it returns a path, or @data thenit's safe to use within .scss/.sass, otherwise it will probably throw.

body {
  background-image: asset_url("img.png @magick:half")
}

*Note: we do not validate your arguments, so if you send a conflicting*argument that results in invalid CSS, you are responsible for that, in*that if you ship us srcset we might or might not throw, depending on how*the threads are ran. So it might ship HTML if you do it wrong, and it will*break your CSS, this is by design so that if possible, in the future, we canallow more flexibility, or so that plugins can change based on arguments.

Listing Assets in Liquid

We provide all your assets as a hash of Liquid Drops so you canget basic info that we wish you to have access to without having toprepare the class. Note: The keys in the assets array are thenames of the original files, e.g., use *.scss instead of *.css.

{{ assets["bundle.css"].content_type }} => "text/css"
{{ assets["images.jpg"].width  }} => 62
{{ assets["images.jpg"].height }} => 62

The current list of available accessors:

Looping

{% for k,v in assets %}
  {{ k }}
{% endfor %}

Dynamic

Using Liquid Drop assets, you can check whether an asset is present.

{% if assets[page.image] %}{% img '{{ page.image }}' %}
{% else %}
  {% img default.jpg %}
{% endif %}

Filter

{{ src | asset:"@magick:double magick:quality=92" }}

Hooks

Example

Jekyll::Assets::Hook.register :env, :before_init do
  append_path "myPluginsCustomPath"
end

Jekyll::Assets::Hook.register :config, :init do |c|
  c.deep_merge!({
    plugins: {
      my_plugin: {
        opt: true
      }
    }
  })
end

Plugin Hooks

Your plugin can also register it's own hooks on our Hook system,so that you can trigger hooks around your stuff as well,this is useful for extensive plugins that want more power.

Jekyll::Assets::Hook.add_point(
  :plugin, :hook
)

Jekyll::Assets::Hook.trigger(:plugin, :hook)  { |v| v.call(:arg) }
Jekyll::Assets::Hook.trigger(:plugin, :hook) do |v|
  instance_eval(&v)
end

Default Plugins

Google Closure Alternates

gem "crass"

Once crass is added, we will detect vendor prefixes, andadd /* @alternate */ to them, with or without compressionenabled, and with protections against compression stripping.

Font Awesome

gem "font-awesome-sass"

@import "font-awesome-sprockets";
@import "font-awesome";
html {
  // ...
}

CSS Auto-Prefixing

gem "autoprefixer-rails"

assets:
  autoprefixer:
    browsers:
    - "last 2 versions"
    - "IE > 9"

Bootstrap

gem "bootstrap-sass" # 3.x
gem "bootstrap"      # 4.x

@import 'bootstrap';
html {
  // ...
}

//=require _bootstrap.css
//=require bootstrap/_reboot.css

ImageMagick

gem "mini_magick"

Args

See the MiniMagick docsto get an idea what <value> can be.

^* magick:format requires an ext or a valid MIME content type like image/jpeg or .jpg. We will ImageMagick -format on your behalf with that information by getting the extension.

ImageOptim

gem "image_optim"
gem "image_optim_pack" # Optional

Configuration

assets:
  plugins:
    img:
      optim:
        {}

Check the ImageOptim to get idea about configuration options, and to get a list of stuff you need to install on your system to use it, if you do not wish to use "image_optim_pack".

To disable ImageOptim (i.e. for development builds), use following configuration:

assets:
  plugins:
    img:
      optim: false

Args

By default @optim will use the default jekyll, otherwise you can provide optim=preset and have it used that preset. ImageOptim provides advanced, and default as their default presets, you can define your own preset via Jekyll Assets configuration listed above.

LibVIPS

gem "ruby-vips"

The "ruby-vips" gem requires a functional installof (libvips)[https://github.com/libvips/libvips/].

Args

vips:resize

Accepts an argument of either 'width', 'x' or 'x'.All resize processes keep the original aspect ratio so width andheight are used to specify the bounding box for the resize process.

If no height is specified the image is resized to fit withing abounding box of 'width' x 'width'. Similarly specifying just aheight sets the bounding box for the resize to 'height' x 'height'.This form only exists for compatibility with the "magick" plugin.

{% asset img.png vips:resize='x100' %}
{% asset img.png vips:resize='100x50' %}
{% asset img.png vips:resize='100x' %}

vips:format

Convert the image to the specified format. Format supportdepends on the compile options of the libvips library. Format isspecified as the file extension such as '.jpg', '.webp' or '.png'.

{% asset image.png vips:format='.webp' %}

vips:crop

Only has any effect when combined with "vips:resize". Usethe following arguments (all except "fill" are documentedhere):

• fill: resize the image to the specified size while maintaining theaspect ratio then fills the "empty" background with blurred versionof the original image
• entropy: use an entropy measure
• high: position the crop towards the high coordinate
• attention: look for features likely to draw human attention
• low: position the crop towards the low coordinate
• centre: crop from the centre
• none: do nothing

{% asset image.jpg vips:resize='100' vips:crop='fill' %}

vips:strip

Removes metadata from images. This is set "true" bydefault, but can be disabled by passing "false".

{% asset image.jpg vips:strip=false %}

Building Your Own Plugins

Globals

HTML