export declare function toBase64(file: globalThis.File): Promise<string>;
/**
 * Convert base64 data-uri to File, return undefine if failed to decode
 * @param dataurl data base64
 * @param filename output's filename
 * @param mimeType output's mimeType
 */
export declare function fromBase64(dataurl: string, filename?: string, mimeType?: string): globalThis.File | undefined;