PostCSS Gradients Interpolation Method

npm install @csstools/postcss-gradients-interpolation-method --save-dev

PostCSS Gradients Interpolation Method lets you use different interpolation methods in CSS gradient functions following CSS Images Module 4.

.example {
    background-image: linear-gradient(in oklch, hsl(0deg 85% 75%) 0%, hsl(180deg 80% 65%) 100%);
}

:root {
    --background-image: linear-gradient(in oklab, hsl(96, 42%, 24%) 0%, hsl(302, 67%, 25%) 100%);
}

/* becomes */

.example {
    background-image: linear-gradient(rgb(245, 137, 137) 0%, rgb(248, 146, 114), rgb(244, 158, 94), rgb(235, 171, 82), rgb(220, 185, 81), rgb(201, 199, 95), rgb(177, 211, 118), rgb(151, 221, 146), rgb(125, 229, 177), rgb(103, 235, 208), rgb(94, 237, 237) 100%);
    background-image: linear-gradient(in oklch, hsl(0deg 85% 75%) 0%, hsl(180deg 80% 65%) 100%);
}

:root {
    --background-image: linear-gradient(rgb(56, 87, 35) 0%, rgb(64, 83, 46), rgb(70, 79, 54), rgb(76, 74, 62), rgb(82, 69, 68), rgb(86, 64, 75), rgb(91, 58, 81), rgb(95, 51, 87), rgb(99, 44, 93), rgb(103, 34, 98), rgb(106, 21, 104) 100%);
}

@supports (background: linear-gradient(in oklch, red 0%, red 0% 1%, red 2%)) {
:root {
    --background-image: linear-gradient(in oklab, hsl(96, 42%, 24%) 0%, hsl(302, 67%, 25%) 100%);
}
}

Shortcomings

[!CAUTION] Color stops with only a color or only an interpolation hint are not supported.

For best results you should always provide at least the color and position for each color stop. Double position color stops are supported.

.foo {
    /* Only a color: can't transform */
    background-image: linear-gradient(in oklch, black 0%, green, blue 100%);

    /* Only an interpolation hint: can't transform */
    background-image: linear-gradient(in oklch, black 0%, 25%, blue 100%);
}

[!CAUTION] Variable colors are not supported. We can not mix colors when the color is a variable.

.foo {
    --red: red;
    /* Color stop variable : can't transform */
    background-image: linear-gradient(in oklch, black 0%, var(--red), blue 100%);
}

Usage

Add PostCSS Gradients Interpolation Method to your project:

npm install postcss @csstools/postcss-gradients-interpolation-method --save-dev

Use it as a PostCSS plugin:

const postcss = require('postcss');
const postcssGradientsInterpolationMethod = require('@csstools/postcss-gradients-interpolation-method');

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

Options

preserve

The preserve option determines whether the original notation is preserved. By default, it is preserved.

postcssGradientsInterpolationMethod({ preserve: false })

.example {
    background-image: linear-gradient(in oklch, hsl(0deg 85% 75%) 0%, hsl(180deg 80% 65%) 100%);
}

:root {
    --background-image: linear-gradient(in oklab, hsl(96, 42%, 24%) 0%, hsl(302, 67%, 25%) 100%);
}

/* becomes */

.example {
    background-image: linear-gradient(rgb(245, 137, 137) 0%, rgb(248, 146, 114), rgb(244, 158, 94), rgb(235, 171, 82), rgb(220, 185, 81), rgb(201, 199, 95), rgb(177, 211, 118), rgb(151, 221, 146), rgb(125, 229, 177), rgb(103, 235, 208), rgb(94, 237, 237) 100%);
}

:root {
    --background-image: linear-gradient(rgb(56, 87, 35) 0%, rgb(64, 83, 46), rgb(70, 79, 54), rgb(76, 74, 62), rgb(82, 69, 68), rgb(86, 64, 75), rgb(91, 58, 81), rgb(95, 51, 87), rgb(99, 44, 93), rgb(103, 34, 98), rgb(106, 21, 104) 100%);
}

enableProgressiveCustomProperties

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

[!NOTE] 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.

postcssGradientsInterpolationMethod({ enableProgressiveCustomProperties: false })

.example {
    background-image: linear-gradient(in oklch, hsl(0deg 85% 75%) 0%, hsl(180deg 80% 65%) 100%);
}

:root {
    --background-image: linear-gradient(in oklab, hsl(96, 42%, 24%) 0%, hsl(302, 67%, 25%) 100%);
}

/* becomes */

.example {
    background-image: linear-gradient(rgb(245, 137, 137) 0%, rgb(248, 146, 114), rgb(244, 158, 94), rgb(235, 171, 82), rgb(220, 185, 81), rgb(201, 199, 95), rgb(177, 211, 118), rgb(151, 221, 146), rgb(125, 229, 177), rgb(103, 235, 208), rgb(94, 237, 237) 100%);
    background-image: linear-gradient(in oklch, hsl(0deg 85% 75%) 0%, hsl(180deg 80% 65%) 100%);
}

:root {
    --background-image: linear-gradient(rgb(56, 87, 35) 0%, rgb(64, 83, 46), rgb(70, 79, 54), rgb(76, 74, 62), rgb(82, 69, 68), rgb(86, 64, 75), rgb(91, 58, 81), rgb(95, 51, 87), rgb(99, 44, 93), rgb(103, 34, 98), rgb(106, 21, 104) 100%);
    --background-image: linear-gradient(in oklab, hsl(96, 42%, 24%) 0%, hsl(302, 67%, 25%) 100%);
}

Custom properties do not fallback to the previous declaration