import { SystemGroupId } from "./constants";
export declare function arrayToBase64(data: Uint8Array): string;
export declare function base64ToUint8Array(base64: string): Uint8Array;
export declare function arrayBufferToBase64(buffer: ArrayBuffer): string;
export declare function base64ToArrayBuffer(base64: string): ArrayBuffer;
export declare function base64ToUtf8(base64: string): string;
export declare function utf8ToBase64(str: string): string;
export declare function concatArrayBuffers(a: ArrayBuffer, b: ArrayBuffer): ArrayBuffer;
export declare function concatUint8Arrays(a: Uint8Array, b: Uint8Array): Uint8Array;
/**
 * Accepts any photo input format and always returns a base64 data-URL string.
 *
 * Supported inputs:
 *  - Already a base64 data-URL  → returned as-is
 *  - Raw base64 string (no prefix) → prefixed with a generic data-URL header
 *  - HTTP/HTTPS URL              → fetched and converted to base64
 *  - Blob / File                 → read via FileReader
 *  - ArrayBuffer / Uint8Array    → converted directly
 */
export declare function normalizePhotoToBase64(input: unknown): Promise<string>;
export declare function isSystemGroupId(id: string): id is SystemGroupId;