export type Rgb = {
    r: number;
    g: number;
    b: number;
};
export type Hsl = {
    h: number;
    s: number;
    l: number;
};
export declare function hexToRgb(hex: string): Rgb;
/** Alpha in 0..1. `#rgb`/`#rrggbb` read as fully opaque (`a: 1`); `#rgba`/`#rrggbbaa` carry their alpha. */
export declare function hexToRgba(hex: string): Rgb & {
    a: number;
};
export declare function compositeOver(foreground: string, backdrop: string): string;
export declare function rgbToHex({ r, g, b }: Rgb): string;
export declare function rgbToHsl({ r, g, b }: Rgb): Hsl;
export declare function hslToRgb({ h, s, l }: Hsl): Rgb;
export declare const hexToHsl: (hex: string) => Hsl;
export declare const hslToHex: (hsl: Hsl) => string;
/** Re-lights a color while keeping its hue (and, unless overridden, its saturation). */
export declare function withLightness(hex: string, lightness: number, saturation?: number): string;
/** Linear RGB blend. `weight` is how much of `b` to take (0 → a, 1 → b). */
export declare function mix(a: string, b: string, weight: number): string;
/** WCAG 2.1 relative luminance. */
export declare function relativeLuminance(hex: string): number;
/** WCAG 2.1 contrast ratio, 1–21. AA body text needs >= 4.5. */
export declare function contrastRatio(a: string, b: string): number;