@csstools/postcss-image-set-function

⚠️ PostCSS image-set-polyfill() has been deprecated in favour of postcss-image-set-function. ⚠️

PostCSS image-set() Function

PostCSS image-set() Function lets you display resolution-dependent images using the image-set() function in CSS, following the CSS Images specification.

.example {
  background-image: image-set(
    url(img.png) 1x,
    url([e-mail]) 2x,
    url([e-mail]) 600dpi
  );
}

/* becomes */

@media (-webkit-min-device-pixel-ratio: 1), (min-resolution: 96dpi) {
  .example {
    background-image: url(img.png);
  }
}

@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
  .example {
    background-image: url([e-mail]);
  }
}


@media (-webkit-min-device-pixel-ratio: 6.25), (min-resolution: 600dpi) {
  .example {
    background-image: url([e-mail]);
  }
}

.example {
  background-image: image-set(
    url(img.png) 1x,
    url([e-mail]) 2x,
    url([e-mail]) 600dpi
  );
}

Usage

Add PostCSS image-set() Function to your build tool:

npm install postcss-image-set-function --save-dev

Node

Use PostCSS image-set() Function to process your CSS:

import postcssImageSetFunction from 'postcss-image-set-function';

postcssImageSetFunction.process(YOUR_CSS, /* processOptions */, /* pluginOptions */);

PostCSS

Add PostCSS to your build tool:

npm install postcss --save-dev

Use PostCSS image-set() Function as a plugin:

import postcss from 'gulp-postcss';
import postcssImageSetFunction from 'postcss-image-set-function';

postcss([
  postcssImageSetFunction(/* pluginOptions */)
]).process(YOUR_CSS);

Webpack

Add PostCSS Loader to your build tool:

npm install postcss-loader --save-dev

Use PostCSS image-set() Function in your Webpack configuration:

import postcssImageSetFunction from 'postcss-image-set-function';

module.exports = {
  module: {
    rules: [
      {
        test: /\.css$/,
        use: [
          'style-loader',
          { loader: 'css-loader', options: { importLoaders: 1 } },
          { loader: 'postcss-loader', options: {
            ident: 'postcss',
            plugins: () => [
              postcssImageSetFunction(/* pluginOptions */)
            ]
          } }
        ]
      }
    ]
  }
}

Gulp

Add Gulp PostCSS to your build tool:

npm install gulp-postcss --save-dev

Use PostCSS image-set() Function in your Gulpfile:

import postcss from 'gulp-postcss';
import postcssImageSetFunction from 'postcss-image-set-function';

gulp.task('css', () => gulp.src('./src/*.css').pipe(
  postcss([
    postcssImageSetFunction(/* pluginOptions */)
  ])
).pipe(
  gulp.dest('.')
));

Grunt

Add Grunt PostCSS to your build tool:

npm install grunt-postcss --save-dev

Use PostCSS image-set() Function in your Gruntfile:

import postcssImageSetFunction from 'postcss-image-set-function';

grunt.loadNpmTasks('grunt-postcss');

grunt.initConfig({
  postcss: {
    options: {
      use: [
       postcssImageSetFunction(/* pluginOptions */)
      ]
    },
    dist: {
      src: '*.css'
    }
  }
});

Options

preserve

The preserve option determines whether the original declaration using image-set() is preserved. By default, it is preserved.

postcssImageSetFunction({ preserve: false })

.example {
  background-image: image-set(
    url(img.png) 1x,
    url([e-mail]) 2x,
    url([e-mail]) 600dpi
  );
}

/* becomes */

@media (-webkit-min-device-pixel-ratio: 1), (min-resolution: 96dpi) {
  .example {
    background-image: url(img.png);
  }
}

@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
  .example {
    background-image: url([e-mail]);
  }
}


@media (-webkit-min-device-pixel-ratio: 6.25), (min-resolution: 600dpi) {
  .example {
    background-image: url([e-mail]);
  }
}

onvalid

The oninvalid option determines how invalid usage of image-set() should be handled. By default, invalid usages of image-set() are ignored. They can be configured to display a warning or throw an error.

postcssImageSetFunction({ oninvalid: 'warning' }) // warn on invalid usages

postcssImageSetFunction({ oninvalid: 'throw' }) // throw on invalid usages