sneak
e623fd2015
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exif() takes the altitude from the GPSAltitude tag and negates it only when GPSAltitudeRef is 1, so a file with GPSAltitude and no GPSAltitudeRef keeps its altitude, above sea level. A test covers that file. backup-metadata --exif keeps the EXIF tags exifreader has no name for. The comments in src/exif.ts say the thumbnail's tags are not kept and that a tag with several values computes to an array. Model: opus-5-5
200 lines
7.8 KiB
TypeScript
200 lines
7.8 KiB
TypeScript
/**
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* Tests for reading EXIF (`src/exif.ts`) and the image metadata
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* `quak backup-metadata --exif` records.
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*
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* The originals come from users' libraries, so a truncated or corrupt file
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* must neither hang the read nor throw out of it: `readPhotoExif` gives `{}`,
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* and `backup-metadata` tells an EXIF block it cannot read apart from a file
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* that simply has no EXIF, carrying the reason in `exifError`. Each JPEG below
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* is a short hand-built byte array; the HEIC is a real file.
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*/
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import { describe, expect, it } from "vitest";
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import { readPhotoExif } from "../../src/exif.js";
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import { extractImageMetadata } from "../../src/metadata-backup.js";
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import { HEIC_WITH_EXIF } from "../exif-heic.js";
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const SOI = [0xff, 0xd8]; // start of image
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const SOS = [0xff, 0xda, 0x00, 0x02]; // start of scan
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const EXIF_HEADER = [0x45, 0x78, 0x69, 0x66, 0x00, 0x00]; // "Exif\0\0"
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const APP0 = [0xff, 0xe0, 0x00, 0x04, 0x00, 0x00];
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const ZERO_LENGTH_APP0 = [0xff, 0xe0, 0x00, 0x00];
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// A big-endian TIFF block with one IFD entry: Orientation (0x0112), SHORT, 6.
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const TIFF_ORIENTATION_6 = [
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0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08, 0x00, 0x01, 0x01, 0x12,
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0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00,
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];
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// A big-endian TIFF block holding Orientation 6 and DateTimeOriginal
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// "0000:00:00 00:00:00", which a camera with an unset clock writes.
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const TIFF_UNSET_DATE = [
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...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
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// The first IFD, at 8: two entries, then no next IFD.
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...[0x00, 0x02],
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// Orientation (0x0112), SHORT, 6.
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...[0x01, 0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00],
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// The Exif IFD's offset (0x8769), LONG, 38.
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...[0x87, 0x69, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x26],
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...[0x00, 0x00, 0x00, 0x00],
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// The Exif IFD, at 38: one entry, then no next IFD.
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...[0x00, 0x01],
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// DateTimeOriginal (0x9003), 20 ASCII bytes at 56.
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...[0x90, 0x03, 0x00, 0x02, 0x00, 0x00, 0x00, 0x14, 0x00, 0x00, 0x00, 0x38],
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...[0x00, 0x00, 0x00, 0x00],
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...new TextEncoder().encode("0000:00:00 00:00:00\0"), // at 56
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];
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// A big-endian TIFF block holding a GPSAltitude of 12.5 m and no
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// GPSAltitudeRef.
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const TIFF_ALTITUDE_WITHOUT_REF = [
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...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
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// The first IFD, at 8: one entry, then no next IFD.
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...[0x00, 0x01],
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// The GPS IFD's offset (0x8825), LONG, 26.
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...[0x88, 0x25, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x1a],
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...[0x00, 0x00, 0x00, 0x00],
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// The GPS IFD, at 26: one entry, then no next IFD.
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...[0x00, 0x01],
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// GPSAltitude (0x0006), one RATIONAL at 44.
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...[0x00, 0x06, 0x00, 0x05, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x2c],
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...[0x00, 0x00, 0x00, 0x00],
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...[0x00, 0x00, 0x00, 0x19, 0x00, 0x00, 0x00, 0x02], // 25/2, at 44
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];
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// An APP1 segment whose length field matches its data.
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const app1 = (data: number[]): number[] => {
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const len = data.length + 2;
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return [0xff, 0xe1, len >> 8, len & 0xff, ...data];
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};
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const bytes = (...parts: number[][]): Uint8Array =>
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new Uint8Array(parts.flat());
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describe("readPhotoExif", () => {
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it("reads the common fields of a valid JPEG", () => {
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const data = [...EXIF_HEADER, ...TIFF_ORIENTATION_6];
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expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
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orientation: 6,
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});
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});
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it("gives no dateTimeOriginal for a DateTimeOriginal of 0000:00:00 00:00:00", () => {
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const data = [...EXIF_HEADER, ...TIFF_UNSET_DATE];
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expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
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orientation: 6,
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});
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});
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it("reads a GPSAltitude without GPSAltitudeRef as above sea level", () => {
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const data = [...EXIF_HEADER, ...TIFF_ALTITUDE_WITHOUT_REF];
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expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
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gpsAltitude: 12.5,
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});
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});
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it.each([
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[
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"a file that is not an image",
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new TextEncoder().encode("just some text, not an image"),
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],
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[
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"a PNG without EXIF",
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bytes([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
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],
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["a JPEG without EXIF", bytes(SOI, APP0, SOS)],
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// A length under 8 cannot hold the six-byte "Exif\0\0" header. This one
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// has length 7 and holds only "Exif\0", so a read past its end would
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// take the next segment's bytes as EXIF.
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[
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"an APP1 segment too short to hold the Exif header",
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bytes(SOI, app1(EXIF_HEADER.slice(0, 5)), SOS),
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],
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[
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"an APP1 segment holding just the Exif header",
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bytes(SOI, app1(EXIF_HEADER), SOS),
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],
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[
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"a JPEG truncated inside a segment header",
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bytes(SOI, [0xff, 0xe1, 0x00]),
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],
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["a JPEG that ends before the image data", bytes(SOI, APP0)],
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// A length of 0 would step a scan by 2 bytes at a time through the
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// rest of the file, reading garbage as markers.
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[
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"a zero-length segment",
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bytes(
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SOI,
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ZERO_LENGTH_APP0,
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ZERO_LENGTH_APP0,
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ZERO_LENGTH_APP0,
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ZERO_LENGTH_APP0,
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SOS,
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),
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],
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["a segment length of 1", bytes(SOI, [0xff, 0xe0, 0x00, 0x01], SOS)],
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// APP1 claims 0x4000 bytes but only the "Exif\0\0" header follows.
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[
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"a segment length that runs past the end of the file",
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bytes(SOI, [0xff, 0xe1, 0x40, 0x00], EXIF_HEADER),
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],
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// "XX" where the TIFF byte order belongs.
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[
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"an EXIF block that cannot be parsed",
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bytes(SOI, app1([...EXIF_HEADER, 0x58, 0x58]), SOS),
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],
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])("returns no fields for %s", (_, input) => {
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expect(readPhotoExif(input)).toStrictEqual({});
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});
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});
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describe("extractImageMetadata", () => {
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it("parses EXIF from a valid JPEG", () => {
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const meta = extractImageMetadata(
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bytes(SOI, app1([...EXIF_HEADER, ...TIFF_ORIENTATION_6]), SOS),
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);
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expect(meta?.exifError).toBeUndefined();
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expect(meta?.exif).toMatchObject({ Orientation: { value: 6 } });
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});
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it("parses EXIF from a HEIC", () => {
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const meta = extractImageMetadata(HEIC_WITH_EXIF);
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expect(meta?.exifError).toBeUndefined();
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expect(meta?.exif).toMatchObject({
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Make: { value: ["Canon"] },
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Model: { value: ["EOS R5"] },
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DateTimeOriginal: { value: ["2021:07:15 14:30:00"] },
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Orientation: { value: 6 },
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GPSLatitudeRef: { value: ["N"] },
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});
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});
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it("returns nothing for a file that is not an image", () => {
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const text = new TextEncoder().encode("just some text, not an image");
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expect(extractImageMetadata(text)).toBeUndefined();
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});
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it("records the reason when the JPEG is malformed", () => {
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const meta = extractImageMetadata(
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bytes(SOI, [0xff, 0xe1, 0x40, 0x00], EXIF_HEADER),
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);
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expect(meta?.exif).toBeUndefined();
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expect(meta?.exifError).toBe(
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"no tag could be read from the EXIF block",
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);
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});
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it("keeps the raw bytes and the reason when EXIF cannot be parsed", () => {
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// The raw bytes are the whole EXIF block as exifreader finds it: for a
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// JPEG, the APP1 segment, marker and length included.
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const segment = app1([...EXIF_HEADER, 0x58, 0x58]);
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const meta = extractImageMetadata(bytes(SOI, segment, SOS));
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expect(meta?.exif).toBeUndefined();
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expect(meta?.exifRaw).toBe(Buffer.from(segment).toString("base64"));
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expect(meta?.exifError).toBe(
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"no tag could be read from the EXIF block",
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);
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});
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});
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