simonsmith / postcss-at2x

Simplify handling of retina images in CSS

postcss-at2x

Ported from rework-plugin-at2x

Installation

$ npm install postcss postcss-at2x --save-dev

Usage

const fs = require('fs');
const postcss = require('postcss');
const at2x = require('postcss-at2x');

const input = fs.readFileSync('input.css', 'utf8');

const output = postcss()
  .use(at2x())
  .process(input)
  .then(result => console.log(result.css));

.at2x()

Adds at-2x keyword to background and background-image declarations to add retina support for images.

Input

.multi {
  background: url(http://example.com/image.png),
              linear-gradient(to right, rgba(255, 255, 255, 0),  rgba(255, 255, 255, 1)),
              green,
              url(/public/images/cool.png) at-2x;
}

Output

.multi {
  background: url(http://example.com/image.png),
              linear-gradient(to right, rgba(255, 255, 255, 0),  rgba(255, 255, 255, 1)),
              green,
              url(/public/images/cool.png);
}

@media (min-device-pixel-ratio: 1.5), (min-resolution: 144dpi), (min-resolution: 1.5dppx) {
  .multi {
    background-image: url(http://example.com/image.png), 
                      linear-gradient(to right, rgba(255, 255, 255, 0),  rgba(255, 255, 255, 1)), 
                      none,
                      url(/public/images/[e-mail]);
  }
}

Options

identifier (default: "@2x") string

Change the identifier added to retina images, for example [e-mail] can be file-retina.png.

detectImageSize (default: false) boolean

Obtains the image dimensions of the non-retina image automatically and applies them to the background-size property of the retina image.

skipMissingRetina (default: false) boolean

If the retina image cannot be found on the file system it will be skipped and not output into the result CSS.

resolveImagePath function

Get resolved image path for detecting image size. By default, original url value is resolved from current working directory (process.cwd()).

Function receives two arguments: original url value and PostCSS declaration source.

Output

.element {
  background: url(img.jpg) no-repeat;
}

@media (min-device-pixel-ratio: 1.5), (min-resolution: 144dpi), (min-resolution: 1.5dppx) {
  .element {
    background: url([e-mail]) no-repeat;
    background-size: 540px 675px; /* Dimensions of img.jpg */
  }
}

See PostCSS docs for examples for your environment.