exif() returns every EXIF tag in the file (closes #156)

`photo.exif()` now returns every EXIF tag in the file, as the owner ruled, typed `ExifTags`: each tag keyed by name with `exifreader`'s `id`, `value`, `description` and `computed`. A tag with no name is keyed `undefined-` plus its number, and the embedded thumbnail's tags sit under `Thumbnail`. The thirteen typed methods stay, with the same names and types; each now picks its field from `exif()`'s tags. GPS latitude and longitude are worked out from the GPS tags and their reference tags, and a position with no reference tags gives neither. `backup-metadata --exif` output is unchanged.

Model: opus-5-5
Co-authored-by: clawbot <sneak+clawbot@sneak.cloud>

test/cli/metadata-exif.test.ts

@@ -3,14 +3,18 @@
  * `quak backup-metadata --exif` records.
  *
  * The originals come from users' libraries, so a truncated or corrupt file
- * must neither hang the read nor throw out of it: `readPhotoExif` gives `{}`,
+ * must neither hang the read nor throw out of it: `readAllExifTags` gives `{}`,
  * and `backup-metadata` tells an EXIF block it cannot read apart from a file
  * that simply has no EXIF, carrying the reason in `exifError`. Each JPEG below
  * is a short hand-built byte array; the HEIC is a real file.
  */
 
 import { describe, expect, it } from "vitest";
-import { readPhotoExif } from "../../src/exif.js";
+import {
+    readAllExifTags,
+    readExifTags,
+    readPhotoExif,
+} from "../../src/exif.js";
 import { extractImageMetadata } from "../../src/metadata-backup.js";
 import { HEIC_WITH_EXIF } from "../exif-heic.js";
 
@@ -63,6 +67,51 @@ const TIFF_ALTITUDE_WITHOUT_REF = [
     ...[0x00, 0x00, 0x00, 0x19, 0x00, 0x00, 0x00, 0x02], // 25/2, at 44
 ];
 
+// A big-endian TIFF block holding a GPSLatitude of 33° 30' 0" and a
+// GPSLatitudeRef of "S".
+const TIFF_SOUTHERN_LATITUDE = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // The GPS IFD's offset (0x8825), LONG, 26.
+    ...[0x88, 0x25, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x1a],
+    ...[0x00, 0x00, 0x00, 0x00],
+    // The GPS IFD, at 26: two entries, then no next IFD.
+    ...[0x00, 0x02],
+    // GPSLatitudeRef (0x0001), 2 ASCII bytes: "S".
+    ...[0x00, 0x01, 0x00, 0x02, 0x00, 0x00, 0x00, 0x02, 0x53, 0x00, 0x00, 0x00],
+    // GPSLatitude (0x0002), three RATIONALs at 56.
+    ...[0x00, 0x02, 0x00, 0x05, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x38],
+    ...[0x00, 0x00, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x21, 0x00, 0x00, 0x00, 0x01], // 33/1, at 56
+    ...[0x00, 0x00, 0x00, 0x1e, 0x00, 0x00, 0x00, 0x01], // 30/1
+    ...[0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01], // 0/1
+];
+
+// A big-endian TIFF block holding a GPSLatitude of 40° 26' 46" and a
+// GPSLongitude of 79° 58' 56", and neither GPSLatitudeRef nor GPSLongitudeRef.
+const TIFF_POSITION_WITHOUT_REFS = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: one entry, then no next IFD.
+    ...[0x00, 0x01],
+    // The GPS IFD's offset (0x8825), LONG, 26.
+    ...[0x88, 0x25, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x1a],
+    ...[0x00, 0x00, 0x00, 0x00],
+    // The GPS IFD, at 26: two entries, then no next IFD.
+    ...[0x00, 0x02],
+    // GPSLatitude (0x0002), three RATIONALs at 56.
+    ...[0x00, 0x02, 0x00, 0x05, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x38],
+    // GPSLongitude (0x0004), three RATIONALs at 80.
+    ...[0x00, 0x04, 0x00, 0x05, 0x00, 0x00, 0x00, 0x03, 0x00, 0x00, 0x00, 0x50],
+    ...[0x00, 0x00, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x28, 0x00, 0x00, 0x00, 0x01], // 40/1, at 56
+    ...[0x00, 0x00, 0x00, 0x1a, 0x00, 0x00, 0x00, 0x01], // 26/1
+    ...[0x00, 0x00, 0x00, 0x2e, 0x00, 0x00, 0x00, 0x01], // 46/1
+    ...[0x00, 0x00, 0x00, 0x4f, 0x00, 0x00, 0x00, 0x01], // 79/1, at 80
+    ...[0x00, 0x00, 0x00, 0x3a, 0x00, 0x00, 0x00, 0x01], // 58/1
+    ...[0x00, 0x00, 0x00, 0x38, 0x00, 0x00, 0x00, 0x01], // 56/1
+];
+
 // A big-endian TIFF block holding Orientation 6 and a Make whose value lies
 // past the end of the file.
 const TIFF_MAKE_PAST_END = [
@@ -87,6 +136,27 @@ const TIFF_UNNAMED_TAG = [
     ...[0x00, 0x00, 0x00, 0x00],
 ];
 
+// A big-endian TIFF block holding Orientation 6, and a thumbnail IFD holding
+// its own Orientation 1 and a 4-byte JPEG thumbnail.
+const TIFF_WITH_THUMBNAIL = [
+    ...[0x4d, 0x4d, 0x00, 0x2a, 0x00, 0x00, 0x00, 0x08], // the first IFD at 8
+    // The first IFD, at 8: one entry, then the thumbnail IFD at 26.
+    ...[0x00, 0x01],
+    // Orientation (0x0112), SHORT, 6.
+    ...[0x01, 0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x06, 0x00, 0x00],
+    ...[0x00, 0x00, 0x00, 0x1a],
+    // The thumbnail IFD, at 26: three entries, then no next IFD.
+    ...[0x00, 0x03],
+    // Orientation (0x0112), SHORT, 1.
+    ...[0x01, 0x12, 0x00, 0x03, 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00],
+    // JPEGInterchangeFormat (0x0201), LONG: the thumbnail is at 68.
+    ...[0x02, 0x01, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x44],
+    // JPEGInterchangeFormatLength (0x0202), LONG: 4 bytes.
+    ...[0x02, 0x02, 0x00, 0x04, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x04],
+    ...[0x00, 0x00, 0x00, 0x00],
+    ...[0xff, 0xd8, 0xff, 0xd9], // the thumbnail, at 68: an empty JPEG
+];
+
 // An APP1 segment whose length field matches its data.
 const app1 = (data: number[]): number[] => {
     const len = data.length + 2;
@@ -96,31 +166,90 @@ const app1 = (data: number[]): number[] => {
 const bytes = (...parts: number[][]): Uint8Array =>
     new Uint8Array(parts.flat());
 
+describe("readAllExifTags", () => {
+    it("keys a tag exifreader has no name for by its number", () => {
+        const data = [...EXIF_HEADER, ...TIFF_UNNAMED_TAG];
+        expect(readAllExifTags(bytes(SOI, app1(data), SOS))).toStrictEqual({
+            "undefined-49152": {
+                id: 49152,
+                value: 7,
+                description: 7,
+                computed: 7,
+            },
+        });
+    });
+
+    it("puts the thumbnail's tags under Thumbnail, without its image", () => {
+        const input = bytes(
+            SOI,
+            app1([...EXIF_HEADER, ...TIFF_WITH_THUMBNAIL]),
+            SOS,
+        );
+        // exifreader finds the thumbnail's image.
+        expect(readExifTags(input)?.Thumbnail?.type).toBe("image/jpeg");
+        const tags = readAllExifTags(input);
+        expect(tags.Orientation?.value).toBe(6);
+        expect(Object.keys(tags.Thumbnail ?? {}).sort()).toEqual([
+            "JPEGInterchangeFormat",
+            "JPEGInterchangeFormatLength",
+            "Orientation",
+        ]);
+        expect(tags.Thumbnail?.Orientation?.value).toBe(1);
+        expect(readPhotoExif(tags)).toStrictEqual({ orientation: 6 });
+    });
+});
+
 describe("readPhotoExif", () => {
     it("reads the common fields of a valid JPEG", () => {
         const data = [...EXIF_HEADER, ...TIFF_ORIENTATION_6];
-        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+        expect(
+            readPhotoExif(readAllExifTags(bytes(SOI, app1(data), SOS))),
+        ).toStrictEqual({
             orientation: 6,
         });
     });
 
     it("gives no dateTimeOriginal for a DateTimeOriginal of 0000:00:00 00:00:00", () => {
         const data = [...EXIF_HEADER, ...TIFF_UNSET_DATE];
-        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+        expect(
+            readPhotoExif(readAllExifTags(bytes(SOI, app1(data), SOS))),
+        ).toStrictEqual({
             orientation: 6,
         });
     });
 
     it("reads a GPSAltitude without GPSAltitudeRef as above sea level", () => {
         const data = [...EXIF_HEADER, ...TIFF_ALTITUDE_WITHOUT_REF];
-        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+        expect(
+            readPhotoExif(readAllExifTags(bytes(SOI, app1(data), SOS))),
+        ).toStrictEqual({
             gpsAltitude: 12.5,
         });
     });
 
+    it("reads a GPSLatitude with GPSLatitudeRef S as south of the equator", () => {
+        const data = [...EXIF_HEADER, ...TIFF_SOUTHERN_LATITUDE];
+        expect(
+            readPhotoExif(readAllExifTags(bytes(SOI, app1(data), SOS))),
+        ).toStrictEqual({
+            gpsLatitude: -33.5,
+        });
+    });
+
+    it("gives no gpsLatitude or gpsLongitude without their reference tags", () => {
+        const data = [...EXIF_HEADER, ...TIFF_POSITION_WITHOUT_REFS];
+        const tags = readAllExifTags(bytes(SOI, app1(data), SOS));
+        // The position is read; only its hemisphere is unknown.
+        expect(tags.GPSLatitude?.computed).toStrictEqual([40, 26, 46]);
+        expect(tags.GPSLongitude?.computed).toStrictEqual([79, 58, 56]);
+        expect(readPhotoExif(tags)).toStrictEqual({});
+    });
+
     it("gives no make for a Make whose value lies past the end of the file", () => {
         const data = [...EXIF_HEADER, ...TIFF_MAKE_PAST_END];
-        expect(readPhotoExif(bytes(SOI, app1(data), SOS))).toStrictEqual({
+        expect(
+            readPhotoExif(readAllExifTags(bytes(SOI, app1(data), SOS))),
+        ).toStrictEqual({
             orientation: 6,
         });
     });
@@ -175,8 +304,9 @@ describe("readPhotoExif", () => {
             "an EXIF block that cannot be parsed",
             bytes(SOI, app1([...EXIF_HEADER, 0x58, 0x58]), SOS),
         ],
-    ])("returns no fields for %s", (_, input) => {
-        expect(readPhotoExif(input)).toStrictEqual({});
+    ])("returns no tags and no fields for %s", (_, input) => {
+        expect(readAllExifTags(input)).toStrictEqual({});
+        expect(readPhotoExif(readAllExifTags(input))).toStrictEqual({});
     });
 });