PostCSS Smart Asset

PostCSS plugin to rebase, inline or copy on url().

Installation

$ npm install postcss postcss-smart-asset

Changes over PostCSS-URL

• Changed output of relative URLs so that the harmonize with Webpack. This mainly means that in Webpack world it is pretty common to use relative URLs even inside CSS e.g. use url(./myfile.gif) instead of url(myfile.gif). The last syntax actually lead to some issue during Webpack processing as Webpack would assume that you are referencing an npm package called myfile.gif which is probably not what you thought to do.
• Converted whole test suite from Mocha + Chai to Jest. Made whole test suite asynchronous.
• Migrated source code to EcmaScript modules (ESM). Refactored internal structure.
• Replaced custom eslint definitions with effective linting rules.
• Restructured tests to be side-by-side with implementation code.
• Use of Preppy instead of custom release logic. Offering a ESM bundle now as well.

Basic example - rebase

// dependencies
const fs = require("fs")
const postcss = require("postcss")
const smartAsset = require("postcss-smart-asset")

// css to be processed
const css = fs.readFileSync("input.css", "utf8")

// process css
const output = postcss()
  .use(
    smartAsset({
      url: "rebase"
    })
  )
  .process(css, {
    from: "src/stylesheet/index.css",
    to: "dist/index.css"
  })

before:

.element {
  background: url("images/sprite.png");
}

after:

.element {
  /* rebasing path by new destination */
  background: url("../src/stylesheet/images/sprite.png");
}

Inline

const options = {
  url: "inline"
}

postcss().use(smartAsset(options)).process(css, {
  from: "src/stylesheet/index.css",
  to: "dist/index.css"
})

before:

.element {
  background: url("/images/sprite.png");
  filter: url("/images/circle.svg");
}

after:

.element {
  /* inlined png as base64 */
  background: url("data:image/png;base64,R0lGODlhAQABAJH/AP///wAAAP///wAAACH/C0FET0JFOklSMS4");
  /* inlined svg as encodeURIComponent */
  filter: url("data:image/svg+xml,%3Csvg xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%22%2F%3E");
}

Copy

const options = {
  url: "copy",
  // base path to search assets from
  basePath: path.resolve("node_modules/bootstrap"),
  // dir to copy assets
  assetsPath: "img",
  // using hash names for assets (generates from asset content)
  useHash: true
}

postcss().use(smartAsset(options)).process(css, {
  from: "src/stylesheet/index.css",
  to: "dist/index.css"
})

before:

.element {
  background: url("/images/sprite.png");
}

after:

.element {
  /* copy 'sprite.png' from 'node_modules/bootstrap/images/' to 'dist/img/' */
  /* and rename it by hash function */
  background: url("img/a2ds3kfu.png");
}

Muiltiple options

process first matched option by default. multi: true in custom will processing with other options

const options = [
  { filter: "**/assets/copy/*.png", url: "copy", assetsPath: "img", useHash: true },
  { filter: "**/assets/inline/*.svg", url: "inline" },
  { filter: "**/assets/**/*.gif", url: "rebase" },
  // using custom function to build url
  { filter: "cdn/**/*", url: (asset) => `https://cdn.url/${asset.url}` }
]

postcss().use(smartAsset(options))

Checkout tests for examples.

Options combinations

• rebase - default
• inline
  • basePath - path or array of paths to search assets (relative to from, or absolute)
  • encodeType - base64, encodeURI, encodeURIComponent
  • includeUriFragment - include the fragment identifer at the end of the URI
  • maxSize - file size in kbytes
  • fallback - copy or custom function for files > maxSize
  • ignoreFragmentWarning - do not warn when an SVG URL with a fragment is inlined
  • optimizeSvgEncode - reduce size of inlined svg (IE9+, Android 3+)
• copy
  • basePath - path or array of paths to search assets (relative to from, or absolute)
  • assetsPath - directory to copy assets (relative to to or absolute)
  • useHash - use content hash of file for naming
  • keepName - use filename~hash as filename (assuming useHash is also true)
  • hashOptions - options for hash function
• custom {Function}
  • multi - processing with other options

Options list

url

rebase - (default)

Allow you to fix url() according to postcss to and/or from options (rebase to to first if available, otherwise from or process.cwd()).

inline

Allow you to inline assets using base64 encoding. Can use postcss from option to find ressources.

copy

Allow you to copy and rebase assets according to postcss to, assetsPath and from options (assetsPath is relative to the option to).

url: {Function}

Custom transform function. Takes following arguments:

• asset
  • url - original url
  • pathname - url pathname (url without search or hash)
  • absolutePath - absolute path to asset
  • relativePath - current relative path to asset
  • search - search from url, ex. ?query=1 from ./image.png?query=1
  • hash - hash from url, ex. #spriteLink from ../asset.svg#spriteLink
• dir
  • from - PostCSS option from
  • to - PostCSS option to
  • file - decl file path
• options - plugin options
• decl - related postcss declaration object
• warn - wrapped function result.warn for current decl
• result – PostCSS result object

And should return the transformed url. You can use this option to adjust urls for CDN.

maxSize

(default: 14)

Specify the maximum file size to inline (in kbytes)

ignoreFragmentWarning

(default: false)

Do not warn when an SVG URL with a fragment is inlined. PostCSS-URL does not support partial inlining. The entire SVG file will be inlined. By default a warning will be issued when this occurs.

NOTE: Only files less than the maximum size will be inlined.

filter

A regular expression e.g. /\.svg$/, a minimatch string e.g. '**/*.svg' or a custom filter function to determine wether a file should be inlined.

fallback

The url fallback method to use if max size is exceeded or url contains a hash. Custom transform functions are supported.

includeUriFragment

(default: false)

Specifies whether the URL's fragment identifer value, if present, will be added to the inlined data URI.

basePath

Specify the base path or list of base paths where to search images from

assetsPath

(default: false)

If you specify an assetsPath, the assets files will be copied in that destination

useHash

(default: false)

If set to true the copy method is going to rename the path of the files by a hash name

keepName

(default: false)

If set to true and useHash is also true, the copy method appends the hash to the original file name instead of replacing it

hashOptions

(default: {})

Any options supported by the underlying asset-hash library. Uses defaults of this library by default.

License

Apache License Version 2.0, January 2004

Copyright

Copyright 2014Maxime Thirouin Copyright 2017-2022Sebastian Software GmbH