import type { Ref } from 'vue';
export declare function useWatermark({ appendEl, color, size, }: {
    appendEl?: Ref<HTMLElement | null, HTMLElement | null> | undefined;
    color?: string | undefined;
    size?: {
        width: number;
        height: number;
    } | undefined;
}): {
    setWatermark: (str: string) => void;
    clear: () => void;
};