postcss-lab-function

PostCSS Lab Function

PostCSS Lab Function lets you use lab and lch color functions in CSS, following the CSS Color specification.

.color-lab {
	color: lab(40% 56.6 39);
}

.color-lch {
	color: lch(40% 68.735435 34.568626);
}

/* becomes */

.color {
	color: rgb(179, 35, 35);
	color: color(display-p3 0.64331 0.19245 0.16771);
}

.color-lch {
	color: rgb(179, 35, 35);
	color: color(display-p3 0.64331 0.19245 0.16771);
}

Usage

Add PostCSS Lab Function to your project:

npm install postcss postcss-lab-function --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssLabFunction = require('postcss-lab-function');

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

PostCSS Lab Function runs in all Node environments, with special instructions for:

Node	PostCSS CLI	Webpack	Create React App	Gulp	Grunt

Options

preserve

The preserve option determines whether the original functional color notation is preserved. By default, it is not preserved.

postcssLabFunction({ preserve: true })

.color {
	color: lab(40% 56.6 39);
}

/* becomes */

.color {
	color: rgb(179, 35, 35);
	color: color(display-p3 0.64331 0.19245 0.16771);
	color: lab(40% 56.6 39);
}

enableProgressiveCustomProperties

The enableProgressiveCustomProperties option determines whether the original notation is wrapped with @supports when used in Custom Properties. By default, it is enabled.

⚠️ We only recommend disabling this when you set preserve to false or if you bring your own fix for Custom Properties. See what the plugin does in its README.

postcssLabFunction({ enableProgressiveCustomProperties: false })

:root {
	--firebrick: lab(40% 56.6 39);
}

/* becomes */

:root {
	--firebrick: rgb(178, 34, 34); /* will never be used, not even in older browser */
	--firebrick: color(display-p3 0.64331 0.19245 0.16771); /* will never be used, not even in older browser */
	--firebrick: lab(40% 56.6 39);
}

subFeatures

displayP3

The subFeatures.displayP3 option determines if color(display-p3 ...) is used as a fallback.
By default, it is enabled.

display-p3 can display wider gamut colors than rgb on some devices.

postcssOKLabFunction({
	subFeatures: {
		displayP3: false
	}
})

.color {
	color: lab(40% 56.6 39);
}

/* becomes */

.color {
	color: rgb(179, 35, 35);
	color: lab(40% 56.6 39);
}

Out of gamut colors

Depending on the browser implementation out of gamut colors may be clipped, resulting in a different color.
Fallback values generated by PostCSS Lab Function are always mapped to a close alternative in sRGB.

When setting preserve to true the original values will be used by some browsers and these may be clipped.
Certain browsers will have an incorrect color if this occurs.

If the plugin detects out of gamut colors it will emit a warning :

"lch(95% 210 285)" is out of gamut for "display-p3". When "preserve: true" is set this will lead to unexpected results in some browsers.

To resolve this warning you can use a color that is in gamut for display-p3.

Copyright : color conversions

This software or document includes material copied from or derived from https://github.com/w3c/csswg-drafts/tree/main/css-color-4. Copyright © 2022 W3C® (MIT, ERCIM, Keio, Beihang).