/**
 * ISO 21496-1 binary gain map metadata (de)serialization
 * Based on libultrahdr gainmapmetadata.cpp implementation
 *
 * Layout (big endian):
 * - u16 minimum_version, u16 writer_version
 * - u8 flags (bit 7: multichannel, bit 6: use base colour space, bit 2: backward direction, bit 3: common denominator)
 * - headroom: base_hdr_headroom, alternate_hdr_headroom (unsigned fractions)
 * - per channel: gain_map_min (s), gain_map_max (s), gamma (u), base_offset (s), alternate_offset (s)
 *
 * Fractions are written as numerator + denominator, or numerator only when the common denominator flag is set.
 */
import { type GainMapMetadata } from './types';
/**
 * Namespace identifying an ISO 21496-1 APP2 segment (null terminated)
 */
export declare const ISO_NAMESPACE = "urn:iso:std:iso:ts:21496:-1\0";
/**
 * The version-only payload stored in the primary image (minimum_version = 0, writer_version = 0)
 */
export declare const ISO_VERSION_ONLY: Uint8Array<ArrayBuffer>;
/**
 * Serializes gain map metadata into an ISO 21496-1 binary payload
 * (without namespace), to be stored in the gain map image.
 *
 * Values are already in the expected space: gainMapMin/Max and hdrCapacityMin/Max
 * are log2, gamma and offsets are linear.
 *
 * @param metadata
 * @returns
 */
export declare const encodeISOGainMapMetadata: (metadata: GainMapMetadata) => Uint8Array<ArrayBuffer>;
/**
 * Parses an ISO 21496-1 binary payload (without namespace)
 *
 * @param data
 * @returns the parsed metadata
 * @throws {Error} if the payload is unsupported (version, backward direction) or malformed
 */
export declare const decodeISOGainMapMetadata: (data: Uint8Array) => GainMapMetadata;