/**
 * Colour-accessibility checks for the design system's data-visualisation
 * palettes.
 *
 * These run in CI against the shipped tokens (see `chart.validate.test.ts`) so a
 * palette edit that breaks colour-vision separation fails the build instead of
 * shipping. The maths is ported in-repo deliberately: CI must not depend on a
 * script outside the package.
 *
 * ΔE is Euclidean distance in OKLab x100. The CVD thresholds are calibrated to
 * the Machado-Oliveira-Fernandes (2009) severity-1.0 simulation below — the
 * model is part of the standard, not an implementation detail. Swapping in a
 * different simulation would move borderline pairs and require recalibrating
 * the numbers.
 */
export type CvdKind = 'protan' | 'deutan' | 'tritan';
export type PaletteMode = 'light' | 'dark';
export interface CheckResult {
    ok: boolean;
    report: readonly (readonly [name: string, ok: boolean, detail: string])[];
}
export declare function contrast(a: string, b: string): number;
/** OKLCH lightness and chroma. */
export declare function oklch(hex: string): [number, number];
/** OKLCH hue in degrees, 0-360. */
export declare function okhue(hex: string): number;
export declare function deltaE(a: string, b: string, kind?: CvdKind): number;
export declare function validateCategorical(palette: readonly string[], { mode, surface, pairs, }: {
    mode: PaletteMode;
    surface: string;
    pairs?: 'adjacent' | 'all';
}): CheckResult;
export declare function validateOrdinal(palette: readonly string[], { mode, surface }: {
    mode: PaletteMode;
    surface: string;
}): CheckResult;