/**
 * Pure colour-conversion utilities for the ColorPicker component.
 *
 * This is the ONLY file where hex/rgb literals are permitted (for conversion
 * math). The component file (`color-picker.tsx`) must not contain hex/rgb
 * literals — it references `var(--…)` tokens for its own UI.
 */
export interface HSLA {
    h: number;
    s: number;
    l: number;
    a: number;
}
/** Parse a hex string (#rgb, #rrggbb, #rrggbbaa) into HSLA. */
export declare function hexToHsl(hex: string): HSLA;
/** Convert HSLA to a hex string (#rrggbb or #rrggbbaa when a < 1). */
export declare function hslToHex(hsl: HSLA): string;
/** Convert HSLA to an rgba() string. */
export declare function hslToRgba(hsl: HSLA): string;
/** Format an HSLA value to the specified output format. */
export declare function formatOutput(hsl: HSLA, format: 'hex' | 'hsl' | 'rgba'): string;
/** Parse any supported colour string into HSLA. Returns null on failure. */
export declare function parseInput(value: string): HSLA | null;
/** Relative luminance per WCAG 2.x (0 = black, 1 = white). */
export declare function relativeLuminance(hsl: HSLA): number;
/** WCAG 2.x contrast ratio between two colours. */
export declare function contrastRatio(fg: HSLA, bg: HSLA): number;
/** Meets WCAG AA for normal text (≥ 4.5:1). */
export declare function meetsAA(ratio: number): boolean;
/** Meets WCAG AAA for normal text (≥ 7:1). */
export declare function meetsAAA(ratio: number): boolean;
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