mirror of
https://github.com/codedread/bitjs
synced 2025-10-03 09:39:16 +02:00
234 lines
7 KiB
JavaScript
234 lines
7 KiB
JavaScript
import { ByteStream } from '../../io/bytestream.js';
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/** @enum {number} */
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export const ExifTagNumber = {
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// Tags used by IFD0.
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IMAGE_DESCRIPTION: 0x010e,
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MAKE: 0x010f,
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MODEL: 0x0110,
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ORIENTATION: 0x0112,
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X_RESOLUTION: 0x011a,
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Y_RESOLUTION: 0x011b,
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RESOLUTION_UNIT: 0x0128,
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SOFTWARE: 0x0131,
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DATE_TIME: 0x0132,
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WHITE_POINT: 0x013e,
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PRIMARY_CHROMATICITIES: 0x013f,
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Y_CB_CR_COEFFICIENTS: 0x0211,
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Y_CB_CR_POSITIONING: 0x0213,
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REFERENCE_BLACK_WHITE: 0x0214,
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COPYRIGHT: 0x8298,
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EXIF_OFFSET: 0x8769,
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// Tags used by Exif SubIFD.
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EXPOSURE_TIME: 0x829a,
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F_NUMBER: 0x829d,
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EXPOSURE_PROGRAM: 0x8822,
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ISO_SPEED_RATINGS: 0x8827,
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EXIF_VERSION: 0x9000,
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DATE_TIME_ORIGINAL: 0x9003,
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DATE_TIME_DIGITIZED: 0x9004,
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COMPONENT_CONFIGURATION: 0x9101,
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COMPRESSED_BITS_PER_PIXEL: 0x9102,
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SHUTTER_SPEED_VALUE: 0x9201,
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APERTURE_VALUE: 0x9202,
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BRIGHTNESS_VALUE: 0x9203,
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EXPOSURE_BIAS_VALUE: 0x9204,
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MAX_APERTURE_VALUE: 0x9205,
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SUBJECT_DISTANCE: 0x9206,
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METERING_MODE: 0x9207,
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LIGHT_SOURCE: 0x9208,
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FLASH: 0x9209,
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FOCAL_LENGTH: 0x920a,
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MAKER_NOTE: 0x927c,
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USER_COMMENT: 0x9286,
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FLASH_PIX_VERSION: 0xa000,
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COLOR_SPACE: 0xa001,
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EXIF_IMAGE_WIDTH: 0xa002,
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EXIF_IMAGE_HEIGHT: 0xa003,
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RELATED_SOUND_FILE: 0xa004,
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EXIF_INTEROPERABILITY_OFFSET: 0xa005,
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FOCAL_PLANE_X_RESOLUTION: 0xa20e,
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FOCAL_PLANE_Y_RESOLUTION: 0x20f,
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FOCAL_PLANE_RESOLUTION_UNIT: 0xa210,
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SENSING_METHOD: 0xa217,
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FILE_SOURCE: 0xa300,
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SCENE_TYPE: 0xa301,
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// Tags used by IFD1.
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IMAGE_WIDTH: 0x0100,
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IMAGE_LENGTH: 0x0101,
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BITS_PER_SAMPLE: 0x0102,
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COMPRESSION: 0x0103,
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PHOTOMETRIC_INTERPRETATION: 0x0106,
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STRIP_OFFSETS: 0x0111,
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SAMPLES_PER_PIXEL: 0x0115,
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ROWS_PER_STRIP: 0x0116,
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STRIP_BYTE_COUNTS: 0x0117,
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// X_RESOLUTION, Y_RESOLUTION
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PLANAR_CONFIGURATION: 0x011c,
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// RESOLUTION_UNIT
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JPEG_IF_OFFSET: 0x0201,
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JPEG_IF_BYTE_COUNT: 0x0202,
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// Y_CB_CR_COEFFICIENTS
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Y_CB_CR_SUB_SAMPLING: 0x0212,
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// Y_CB_CR_POSITIONING, REFERENCE_BLACK_WHITE
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};
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/** @enum {number} */
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export const ExifDataFormat = {
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UNSIGNED_BYTE: 1,
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ASCII_STRING: 2,
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UNSIGNED_SHORT: 3,
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UNSIGNED_LONG: 4,
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UNSIGNED_RATIONAL: 5,
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SIGNED_BYTE: 6,
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UNDEFINED: 7,
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SIGNED_SHORT: 8,
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SIGNED_LONG: 9,
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SIGNED_RATIONAL: 10,
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SINGLE_FLOAT: 11,
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DOUBLE_FLOAT: 12,
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};
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/**
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* @typedef ExifValue
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* @property {ExifTagNumber} tagNumber The numerical value of the tag.
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* @property {string=} tagName A string representing the tag number.
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* @property {ExifDataFormat} dataFormat The data format.
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* @property {number=} numericalValue Populated for SIGNED/UNSIGNED BYTE/SHORT/LONG/FLOAT.
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* @property {string=} stringValue Populated only for ASCII_STRING.
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* @property {number=} numeratorValue Populated only for SIGNED/UNSIGNED RATIONAL.
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* @property {number=} denominatorValue Populated only for SIGNED/UNSIGNED RATIONAL.
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* @property {number=} numComponents Populated only for UNDEFINED data format.
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* @property {number=} offsetValue Populated only for UNDEFINED data format.
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*/
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/**
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* @param {number} tagNumber
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* @param {string} type
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* @param {number} len
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* @param {number} dataVal
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*/
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function warnBadLength(tagNumber, type, len, dataVal) {
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const hexTag = tagNumber.toString(16);
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console.warn(`Tag 0x${hexTag} is ${type} with len=${len} and data=${dataVal}`);
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}
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/**
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* @param {ByteStream} stream
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* @param {ByteStream} lookAheadStream
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* @param {boolean} debug
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* @returns {ExifValue}
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*/
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export function getExifValue(stream, lookAheadStream, DEBUG = false) {
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const tagNumber = stream.readNumber(2);
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let tagName = findNameWithValue(ExifTagNumber, tagNumber);
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if (!tagName) {
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tagName = `UNKNOWN (0x${tagNumber.toString(16)})`;
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}
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let dataFormat = stream.readNumber(2);
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// Handle bad types for special tags.
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if (tagNumber === ExifTagNumber.EXIF_OFFSET) {
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dataFormat = ExifDataFormat.UNSIGNED_LONG;
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}
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const dataFormatName = findNameWithValue(ExifDataFormat, dataFormat);
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if (!dataFormatName) throw `Invalid data format: ${dataFormat}`;
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/** @type {ExifValue} */
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const exifValue = {
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tagNumber,
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tagName,
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dataFormat,
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};
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let len = stream.readNumber(4);
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switch (dataFormat) {
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case ExifDataFormat.UNSIGNED_BYTE:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekNumber(4));
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}
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exifValue.numericalValue = stream.readNumber(1);
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stream.skip(3);
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break;
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case ExifDataFormat.ASCII_STRING:
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if (len <= 4) {
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exifValue.stringValue = stream.readString(4);
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} else {
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const strOffset = stream.readNumber(4);
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exifValue.stringValue = lookAheadStream.tee().skip(strOffset).readString(len - 1);
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}
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break;
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case ExifDataFormat.UNSIGNED_SHORT:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekNumber(4));
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}
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exifValue.numericalValue = stream.readNumber(2);
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stream.skip(2);
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break;
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case ExifDataFormat.UNSIGNED_LONG:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekNumber(4));
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}
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exifValue.numericalValue = stream.readNumber(4);
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break;
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case ExifDataFormat.UNSIGNED_RATIONAL:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekNumber(4));
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}
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const uratStream = lookAheadStream.tee().skip(stream.readNumber(4));
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exifValue.numeratorValue = uratStream.readNumber(4);
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exifValue.denominatorValue = uratStream.readNumber(4);
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break;
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case ExifDataFormat.SIGNED_BYTE:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekSignedNumber(4));
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}
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exifValue.numericalValue = stream.readSignedNumber(1);
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stream.skip(3);
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break;
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case ExifDataFormat.UNDEFINED:
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exifValue.numComponents = len;
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exifValue.offsetValue = stream.readNumber(4);
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break;
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case ExifDataFormat.SIGNED_SHORT:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekSignedNumber(4));
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}
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exifValue.numericalValue = stream.readSignedNumber(2);
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stream.skip(2);
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break;
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case ExifDataFormat.SIGNED_LONG:
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if (len !== 1) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekSignedNumber(4));
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}
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exifValue.numericalValue = stream.readSignedNumber(4);
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break;
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case ExifDataFormat.SIGNED_RATIONAL:
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if (len !== 1 && DEBUG) {
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warnBadLength(tagNumber, dataFormatName, len, stream.peekNumber(4));
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}
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const ratStream = lookAheadStream.tee().skip(stream.readNumber(4));
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exifValue.numeratorValue = ratStream.readSignedNumber(4);
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exifValue.denominatorValue = ratStream.readSignedNumber(4);
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break;
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default:
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throw `Bad data format: ${dataFormat}`;
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}
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return exifValue;
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}
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/**
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* @param {Object} obj A numeric enum.
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* @param {number} valToFind The value to find.
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* @returns {string|null}
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*/
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function findNameWithValue(obj, valToFind) {
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const entry = Object.entries(obj).find(([k,v]) => v === valToFind);
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return entry ? entry[0] : null;
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}
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