PostCSS Gamut Mapping

npm install @csstools/postcss-gamut-mapping --save-dev

PostCSS Gamut Mapping lets you use wide gamut colors with gamut mapping for specific displays following the CSS Color 4 Specification.

When out of gamut colors are naively clipped the result can be radically different.
A saturated and bright color will be much darker after clipping.

To correctly adjust colors for a narrow gamut display, the colors must be mapped.
This is done by lowering the chroma in oklch until the color is in gamut.

Using the @media (color-gamut) media feature makes it possible to only use the wide gamut colors on displays that support them.

p {
    background-color: oklch(80% 0.05 0.39 / 0.5);
    color: oklch(20% 0.234 0.39 / 0.5);
    border-color: color(display-p3 0 1 0);
}

/* becomes */

p {
    background-color: oklch(80% 0.05 0.39 / 0.5);
    color: rgba(48, 0, 20, 0.5);
    border-color: rgb(0, 247, 79);
}

@media (color-gamut: rec2020) {

@supports (color: oklab(0% 0 0%)) {
p {
    color: oklch(20% 0.234 0.39 / 0.5);
}
}
}

@media (color-gamut: p3) {

@supports (color: color(display-p3 0 0 0%)) {
p {
    border-color: color(display-p3 0 1 0);
}
}
}

Usage

Add PostCSS Gamut Mapping to your project:

npm install postcss @csstools/postcss-gamut-mapping --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssGamutMapping = require('@csstools/postcss-gamut-mapping');

postcss([
    postcssGamutMapping(/* pluginOptions */)
]).process(YOUR_CSS /*, processOptions */);