/**
 * Color Utilities — pure functions for color manipulation and accessibility.
 *
 * Supports hex (#RGB, #RRGGBB, #RRGGBBAA), rgb(), and hsl() formats.
 * WCAG contrast ratio calculations for accessibility compliance.
 *
 * @example
 * const rgb  = hexToRgb('#3b82f6');     // { r: 59, g: 130, b: 246 }
 * const hex  = rgbToHex(59, 130, 246);  // '#3b82f6'
 * const hsl  = hexToHsl('#3b82f6');     // { h: 217, s: 91, l: 60 }
 * const light = lighten('#3b82f6', 20); // '#7cabf9'
 * const ratio = getContrastRatio('#ffffff', '#3b82f6'); // 3.07
 */
export interface RGB {
    r: number;
    g: number;
    b: number;
    a?: number;
}
export interface HSL {
    h: number;
    s: number;
    l: number;
    a?: number;
}
export interface HSV {
    h: number;
    s: number;
    v: number;
}
export type WCAGLevel = 'AA' | 'AAA';
/** Parse a hex string (#RGB, #RRGGBB, #RRGGBBAA) to RGB. Returns null for invalid input. */
export declare function hexToRgb(hex: string): RGB | null;
/** Convert RGB components to a lowercase hex string (e.g. '#3b82f6'). */
export declare function rgbToHex(r: number, g: number, b: number, a?: number): string;
/** Parse a hex string to HSL. Returns null for invalid input. */
export declare function hexToHsl(hex: string): HSL | null;
/** Convert RGB to HSL. */
export declare function rgbToHsl(r: number, g: number, b: number, a?: number): HSL;
/** Convert HSL to a hex string. */
export declare function hslToHex(h: number, s: number, l: number): string;
/** Convert HSL to RGB. */
export declare function hslToRgb(h: number, s: number, l: number): RGB;
/** Convert RGB to HSV. */
export declare function rgbToHsv(r: number, g: number, b: number): HSV;
/** Lighten a hex color by `amount` percent (0-100). */
export declare function lighten(hex: string, amount: number): string;
/** Darken a hex color by `amount` percent (0-100). */
export declare function darken(hex: string, amount: number): string;
/** Saturate a hex color by `amount` percent. */
export declare function saturate(hex: string, amount: number): string;
/** Desaturate a hex color by `amount` percent. */
export declare function desaturate(hex: string, amount: number): string;
/** Rotate the hue of a hex color by `degrees`. */
export declare function rotateHue(hex: string, degrees: number): string;
/**
 * Mix two hex colors together.
 * @param weight 0 = full color1, 100 = full color2. Default 50.
 */
export declare function mix(hex1: string, hex2: string, weight?: number): string;
/** Set the opacity of a hex color (returns 8-char hex). */
export declare function withOpacity(hex: string, alpha: number): string;
/** Invert a hex color. */
export declare function invert(hex: string): string;
/** Calculate relative luminance of a hex color (WCAG 2.1). */
export declare function getLuminance(hex: string): number;
/**
 * Calculate WCAG 2.1 contrast ratio between two colors.
 * @returns ratio between 1 and 21.
 */
export declare function getContrastRatio(fg: string, bg: string): number;
/**
 * Check if a foreground/background pair meets WCAG contrast requirements.
 * - AA normal text: 4.5:1
 * - AA large text (18pt+ or 14pt+ bold): 3:1
 * - AAA normal text: 7:1
 * - AAA large text: 4.5:1
 */
export declare function isAccessible(fg: string, bg: string, level?: WCAGLevel, largeText?: boolean): boolean;
/**
 * Choose the best readable foreground color (black or white) for a given background.
 */
export declare function getReadableColor(bg: string, dark?: string, light?: string): string;
export interface ColorPalette {
    50: string;
    100: string;
    200: string;
    300: string;
    400: string;
    500: string;
    600: string;
    700: string;
    800: string;
    900: string;
}
/**
 * Generate a 10-shade palette (50–900) from a single base color.
 * The base color is placed at shade 500.
 */
export declare function generatePalette(baseHex: string): ColorPalette;
/**
 * Parse any common color string (hex, rgb(), hsl()) to an RGB object.
 * Returns null if unrecognised.
 */
export declare function parseColor(color: string): RGB | null;
/** Convert any supported color string to hex. */
export declare function toHex(color: string): string | null;
/** Format an RGB object as a CSS rgb() / rgba() string. */
export declare function rgbToString(rgb: RGB): string;
/** Format an HSL object as a CSS hsl() / hsla() string. */
export declare function hslToString(hsl: HSL): string;
/** Check if a string is a valid color (hex, rgb, or hsl). */
export declare function isValidColor(color: string): boolean;
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