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https://github.com/jekyll/jekyll-assets

:art: Asset pipelines for Jekyll.
https://github.com/jekyll/jekyll-assets

asset-pipeline assets imagemagick imageoptim jekyll jekyll-assets liquid sass scss sprockets sprockets-4 uglifier

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:art: Asset pipelines for Jekyll.

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README 

        
[![Build Status](https://travis-ci.com/envygeeks/jekyll-assets.svg?branch=master)](https://travis-ci.com/envygeeks/jekyll-assets) [![Maintainability](https://api.codeclimate.com/v1/badges/56f67324553069bf51e7/maintainability)](https://codeclimate.com/github/envygeeks/jekyll-assets/maintainability)



# Jekyll Assets



Jekyll Assets is a drop in [asset

pipeline](http://guides.rubyonrails.org/asset_pipeline.html) that uses

[Sprockets](https://github.com/rails/sprockets) to build specifically

for Jekyll. It utilizes [Sprockets](https://github.com/rails/sprockets),

and [Jekyll](https://jekyllrb.com) to try and achieve a clean, and

extensible assets platform that supports plugins, caching, converting your

assets. It even supports proxying of said assets in a way that does not

interfere with either [Sprockets](https://github.com/rails/sprockets),

or [Jekyll](https://jekyllrb.com), or your own source.  By default you

can add Jekyll Assets to your Gemfile, as a plugin, and have it act as

a drop-in replacement for Jekyll's basic SASS processors, with you only

having to add it to your Gemfile, and updating your ``, and ``.



## Installing



```ruby

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 your

configuration file unless you plan to change a value. *Setting a value makes

it explicit, and shared across both **production**, and **development**.*



```yaml

# _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 %}`, ``



```html

{% asset src @magick:double alt='This is my alt' %}

{% asset src @magick:double alt='This is my alt' %}

This is my alt

This is my alt

```



## Defaults



We provide several defaults that get set when you run an asset, depending on

content 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 can

disable the attribute with `!attribute`, and it will be skipped over.*



```liquid

{% asset img.png !integrity %}

{% asset bundle.css !type   %}

```



### Arguments



Our tags will take any number of arguments, arbitrary or not... and

convert them to HTML, and even attach them to your output if the

HTML processor you use accepts that kind of data.  ***This applies

to anything but hashes, and arrays.*** So adding say, a class, or

id, is as easy as doing `id="val"` inside of your tag arguments.



#### Built In



| Arg | Description | Type | Return Type |

|---|---|---|---|

| `@data` | `data` URI | `*/*` | `text` |

| `@inline` | CSS `` | `text/css` | `text/html` |

| `@path` | Path | `*/*` | `text` |



## Responsive Images

### `<img>` usage

#### Configuration



| Option | Tag Option | Type | Description |

|---|---|---|---|

| automatic | @automatic | Boolean | Upscale & Downscale images |

| automatic_min_width | @min_width | Integer | Stop scaling before this width |

| automatic_scales | scales | String | The scales to use |

| discovery_scales | scales | String | The scales to look for |

| automatic_upscale | @upscale | Boolean | Upscale, the source instead of downscale |

| discovery | @discovery | Boolean | Responsive if an img matching source w/ @<scale>x exists |



***Each option is in the responsive namespace regardless

of whether it's inside of the tag, or configuration.***



#### Example



```liquid

{% asset img.png @pic

    srcset:max-width="200"

    srcset:min-width="200"

    srcset:scales=1x

    srcset:scales=2x

    srcset:scales=3x

        %}

```



```html

<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 responsive

images if we can find assets that match your scales based on the source

file.  For example if you do `{% asset img.png responsive:discovery

responsive:scales=1x responsive:scales=1.5x responsive:scales=2x %}` then

we will expect `[email protected]` and `img.png@2x` to exist.  For any image

that doesn't exist it will be skipped, and that scale will not be included!



#### Automatic



Automatic responsive images/scaling can either upscale, or downscale.  This

is useful if you have a ton of images for blog posts, and you always want to

provide 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`, `1.5x`

and `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 source

will 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 also

support Liquid pre-processing (with your Jekyll context) of most files if they

end with `.liquid`.  This will also give you access to our filters as well as

their filters, and Jekyll's filters, and any tags that are globally available.



```liquid

{% asset '{{ site.bg_img }}' %}

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

{% asset {{\ site.bg_img\ }} %}

```



### `.sass`, `.scss`



```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 processing

we do.  Depending on where you do it, you might or might not also have

access to your local (page) context as well. You can also do whatever you

like, and be as dynamic as you like, including full loops, and conditional

Liquid, 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, we

have opted to only allow the default extension of `.ext.liquid` when running

on "Old Sprockets" (AKA 3.x.)  If you would like Syntax + Liquid you should

opt 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 JS

*you should use a Sprockets `//require=`, Sprockets does not integrate that

*deeply 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 of

SCSS.  All other helpers that Sprockets themselves provide will use our

`asset_path` helper, so you can use them like normal, *including with Liquid*



```scss

body {

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

}

```



### Proxies, and Other Arguments



Any argument that is supported by our regular tags, is also supported by

our `.sass`/`.scss` helpers, with a few obvious exceptions (like `srcset`).

 This means that you can wrap your assets into `magick` if you wish, or

`imageoptim` or any other proxy that is able to spit out a path for you

to use.  The general rule is, that if it returns a path, or `@data` then

it's safe to use within `.scss`/`.sass`, otherwise it will probably throw.



```scss

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 can

*allow 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 can

get basic info that we wish you to have access to without having to

prepare the class. **Note:** The keys in the `assets` array are the

names of the original files, e.g., use `*.scss` instead of `*.css`.



```liquid

{{ assets["bundle.css"].content_type }} => "text/css"

{{ assets["images.jpg"].width  }} => 62

{{ assets["images.jpg"].height }} => 62

```



The current list of available accessors:



| Method         | Description                |

| -------------- | -------------------------- |

| `content_type` | The RFC content type       |

| `filename`     | The full path to the asset |

| `height`       | The asset height           |

| `width`        | The asset width            |

| `digest_path`  | The prefixed path          |

| `integrity`    | The SRI hash               |



### Looping



```liquid

{% for k,v in assets %}

  {{ k }}

{% endfor %}

```



### Dynamic



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



```liquid

{% if assets[page.image] %}{% img '{{ page.image }}' %}

{% else %}

  {% img default.jpg %}

{% endif %}

```



## Filter



```liquid

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

```



## Hooks



| Point | Name | Instance | Args |

| ---| --- | --- | --- |

| `:env` | `:before_init` | ✔ | ✗ |

| `:env` | `:after_init` | ✔ | ✗ |

| `:env` | `:after_write` | ✔ | ✗ |

| `:config` | `:before_merge` | ✗ | `Config{}` |

| `:asset` | `:before_compile` | ✗ | `Asset`, `Manifest` |

| `:asset` | `:after_compression` | ✗ | input{}, output{}, type=*/* |



### Example



```ruby

Jekyll::Assets::Hook.register :env, :before_init do

  append_path "myPluginsCustomPath"

end

```



```ruby

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.



```ruby

Jekyll::Assets::Hook.add_point(

  :plugin, :hook

)

```



```ruby

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, and

add `/* @alternate */` to them, with or without compression

enabled, and with protections against compression stripping.



### Font Awesome



```ruby

gem "font-awesome-sass"

```



```scss

@import "font-awesome-sprockets";

@import "font-awesome";

html {

  // ...

}

```



### CSS Auto-Prefixing



```ruby

gem "autoprefixer-rails"

```



```yml

assets:

  autoprefixer:

    browsers:

    - "last 2 versions"

    - "IE > 9"

```



### Bootstrap



```ruby

gem "bootstrap-sass" # 3.x

gem "bootstrap"      # 4.x

```



```scss

@import 'bootstrap';

html {

  // ...

}

```



```scss

//=require _bootstrap.css

//=require bootstrap/_reboot.css

```



### ImageMagick



```ruby

gem "mini_magick"

```



#### Args



See the [MiniMagick docs](https://github.com/minimagick/minimagick#usage)

to get an idea what `<value>` can be.



| Name                        | Accepts Value |

| --------------------------- | ------------- |

| `magick:compress`           | ✔             |

| `magick:resize`             | ✔             |

| `magick:format`<sup>*</sup> | ✔             |

| `magick:quality`            | ✔             |

| `magick:rotate`             | ✔             |

| `magick:gravity`            | ✔             |

| `magick:crop`               | ✔             |

| `magick:extent`             | ✔             |

| `magick:flip`               | ✔             |

| `magick:background`         | ✔             |

| `magick:transparency`       | ✔             |

| `@magick:double`            | ✗             |

| `@magick:half`              | ✗             |



<sup>\*</sup> *`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



```ruby

gem "image_optim"

gem "image_optim_pack" # Optional

```



#### Configuration



```yml

assets:

  plugins:

    img:

      optim:

        {}

```



Check the [ImageOptim](https://github.com/toy/image_optim#configuration) 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:



```yml

assets:

  plugins:

    img:

      optim: false

```



#### Args



| Name                              | Accepts Value |

| --------------------------------- | ------------- |

| `optim`                           | ✔             |

| `@optim`                          | ✗             |



***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



```ruby

gem "ruby-vips"

```



The "ruby-vips" gem requires a functional install

of (libvips)[https://github.com/libvips/libvips/].



#### Args



| Name                  | Accepts Value |

| --------------------- | ------------- |

| `vips:crop`           | ✔             |

| `vips:resize`         | ✔             |

| `vips:format`         | ✔             |

| `vips:quality`        | ✔             |

| `vips:compression`    | ✔             |

| `@vips:near_lossless` | ✗             |

| `@vips:interlace`     | ✗             |

| `@vips:lossless`      | ✗             |

| `vips:strip`          | ✔             |

| `@vips:strip`         | ✗             |

| `@vips:double`        | ✗             |

| `@vips:half`          | ✗             |



##### vips:resize



Accepts an argument of either 'width', 'x<height>' or '<width>x<height>'.

All resize processes keep the original aspect ratio so width and

height are used to specify the bounding box for the resize process.



If no height is specified the image is resized to fit withing a

bounding box of 'width' x 'width'. Similarly specifying just a

height sets the bounding box for the resize to 'height' x 'height'.

This form only exists for compatibility with the "magick" plugin.



```liquid

{% 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 support

depends on the compile options of the libvips library. Format is

specified as the file extension such as '.jpg', '.webp' or '.png'.



```liquid

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

```



##### vips:crop



Only has any effect when combined with "vips:resize". Use

the following arguments (all except "fill" are documented

[here](http://libvips.github.io/libvips/API/current/libvips-conversion.html#VipsInteresting)):



* fill: resize the image to the specified size while maintaining the

        aspect ratio then fills the "empty" background with blurred version

        of 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



```liquid

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

```



##### vips:strip



Removes metadata from images. This is set "true" by

default, but can be disabled by passing "false".



```liquid

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

```



### Building Your Own Plugins

#### Globals



| Name      | Class                   |

| --------- | ----------------------- |

| `env`    | `Jekyll::Assets::Env`   |

| `args`   | `Liquid::Tag::Parser{}` |

| `jekyll` | `Jekyll::Site`          |

| `asset`  | `Sprockets::Asset`      |



#### HTML



| Name   | Class                      | Type            |

| ------ | -------------------------- | --------------- |

| `@doc` | `Nokogiri:: XML::Document` | `image/svg+xml` |

| `@doc` | `Nokogiri::HTML::Document` | `image/*`       |