export declare const lighten: (hex: string, percent: number) => string;
export declare const darken: (hex: string, percent: number) => string;
/**
 * WCAG relative luminance (0 = black, 1 = white)
 */
export declare function relativeLuminance(hex: string): number;
/**
 * WCAG contrast ratio between two colors (1–21)
 */
export declare function contrastRatio(hex1: string, hex2: string): number;
/**
 * Returns "#ffffff" or "#000000" based on which has better contrast
 * against the given background color.
 *
 * In light mode, white text is slightly favored for borderline colors
 * (e.g. pure red gets white text). In dark mode, black text is favored.
 */
export declare function getContrastTextColor(backgroundHex: string, mode?: "light" | "dark"): string;
/**
 * Adjusts a color to ensure it meets WCAG AA contrast (4.5:1)
 * against the given background. Darkens or lightens in steps.
 */
export declare function ensureContrast(foregroundHex: string, backgroundHex: string, minRatio?: number): string;
