declare class Contrast {
    /**
     * Returns a contrast ratio, which ranges from 1 to 21.
     */
    static ratioOfTones(toneA: number, toneB: number): number;
    private static _ratioOfYs;
    /**
     * Returns a tone >= [tone] that ensures [ratio].
     * Returns -1 if [ratio] cannot be achieved with [tone].
     */
    static lighter(tone: number, ratio: number): number;
    /**
     * Returns a tone <= [tone] that ensures [ratio].
     * Returns -1 if [ratio] cannot be achieved with [tone].
     */
    static darker(tone: number, ratio: number): number;
    /**
     * Returns a tone >= [tone] that ensures [ratio].
     * Returns 100 if [ratio] cannot be achieved with [tone].
     */
    static lighterUnsafe(tone: number, ratio: number): number;
    /**
     * Returns a tone <= [tone] that ensures [ratio].
     * Returns 0 if [ratio] cannot be achieved with [tone].
     */
    static darkerUnsafe(tone: number, ratio: number): number;
}
export default Contrast;
//# sourceMappingURL=contrast.d.ts.map