contrast-with.scss

@use "sass:color";
@use "sass:math";
@use "contrast-ratio-by-name" as *;
@use "is-contrasting" as *;
@use "luminance" as *;
@use "scale-light" as *;
@use "scale-luminance" as *;

/// Adjust color towards a target color until it reaches a contrast ratio
/// @param {Color} $color - Color
/// @param {Color} $target [#fff] - Target color
/// @param {String|Number} $ratio ["AA"] - Contrast ratio
/// @param {Number} $iterations [5] - Iteration count for checking
/// @return {Number}

@function contrast-with($color, $target: #fff, $ratio: "AA", $iterations: 10) {
    $ratio: contrast-ratio-by-name($ratio);
    @if is-contrasting($color, $target, $ratio) == false {
        $luminance: math.clamp(luminance($color), 0, 1);
        $target-luminance: math.clamp(luminance($target), 0, 1);
        $operation: "";
        @if $luminance == $target-luminance {
            @if $luminance > 0.5 {
                $color: color.darken($color, 1%);
                $luminance: luminance($color);
            } @else {
                $color: color.adjust($color, $lightness: 1%);
                $luminance: luminance($color);
            }
        }
        @if math.max($luminance, $target-luminance) == $luminance {
            $target-luminance: (($target-luminance + 0.05) * $ratio - 0.05);
            $operation: lighten;
        } @else {
            $target-luminance: math.div(($target-luminance + 0.05), $ratio) - 0.05;
            $operation: darken;
        }
        @if $target-luminance >= 1 {
            @return #fff;
        } @else if $target-luminance <= 0 {
            @return #000;
        } @else {
            $color: scale-luminance($color, $target-luminance);
            $color: scale-light(
                $color,
                $target,
                $ratio,
                $operation,
                $iterations
            );
        }
    }
    @return $color;
}