fix(core): correct loading of sub array geotags

packages/core/src/__benchmark__/source.file.ts

@@ -1,13 +1,20 @@
-import { readFile, stat } from 'fs/promises';
+import { readFile, stat } from 'node:fs/promises';
+import { gunzip } from 'node:zlib';
+import { promisify } from 'node:util';
 import { Source } from '../source.js';
 
+const gunzipP = promisify(gunzip);
+
 export class TestFileSource implements Source {
   url: URL;
   data: Promise<Buffer>;
 
   constructor(fileName: URL) {
     this.url = fileName;
-    this.data = readFile(this.url);
+    this.data = readFile(this.url).then((buf) => {
+      if (this.url.pathname.endsWith('gz')) return gunzipP(buf);
+      return buf;
+    });
   }
 
   async fetch(offset: number, length: number): Promise<ArrayBuffer> {

packages/core/src/__test__/cog.read.test.ts

@@ -82,4 +82,37 @@ describe('CogRead', () => {
     assert.equal(im.tagsGeo.get(TiffTagGeo.GeogCitationGeoKey), 'NZGD2000');
     assert.deepEqual(await im.fetch(TiffTag.StripByteCounts), [8064, 8064, 8064, 8064, 8064, 8064, 8064, 5040]);
   });
+
+  it('should read sub array ifds', async () => {
+    const source = new TestFileSource(
+      new URL('../../data/east_coast_phase3_2023_AY31_1000_3335.tif.gz', import.meta.url),
+    );
+    const tiff = await CogTiff.create(source);
+
+    assert.equal(tiff.images.length, 5);
+    const im = tiff.images[0];
+
+    assert.equal(im.isGeoTagsLoaded, true);
+    assert.equal(im.epsg, 2193);
+    assert.equal(im.compression, TiffMimeType.Lzw);
+
+    const geoTags = [...im.tagsGeo.keys()].map((key) => TiffTagGeo[key]);
+    assert.deepEqual(geoTags, [
+      'GTModelTypeGeoKey',
+      'GTRasterTypeGeoKey',
+      'GTCitationGeoKey',
+      'GeographicTypeGeoKey',
+      'GeogAngularUnitsGeoKey',
+      'GeogEllipsoidGeoKey',
+      'GeogSemiMajorAxisGeoKey',
+      'GeogSemiMinorAxisGeoKey',
+      'GeogInvFlatteningGeoKey',
+      'GeogTOWGS84GeoKey',
+      'ProjectedCSTypeGeoKey',
+      'PCSCitationGeoKey',
+      'ProjLinearUnitsGeoKey',
+    ]);
+
+    assert.deepEqual(im.tagsGeo.get(TiffTagGeo.GeogTOWGS84GeoKey), [0, 0, 0, 0, 0, 0, 0]);
+  });
 });

packages/core/src/cog.tiff.image.ts

@@ -133,6 +133,7 @@ export class CogTiffImage {
     if (sourceTag.value == null) return;
     const geoTags = sourceTag.value as Uint16Array;
     if (typeof geoTags === 'number') throw new Error('Invalid geo tags found');
+
     for (let i = 4; i <= geoTags[3] * 4; i += 4) {
       const key = geoTags[i] as TiffTagGeo;
       const locationTagId = geoTags[i + 1];
@@ -149,6 +150,9 @@ export class CogTiffImage {
       const count = geoTags[i + 2];
       if (typeof tag.value === 'string') {
         this.tagsGeo.set(key, tag.value.slice(offset, offset + count - 1).trim());
+      } else if (Array.isArray(tag.value)) {
+        if (count === 1) this.tagsGeo.set(key, tag.value[offset]);
+        else this.tagsGeo.set(key, tag.value.slice(offset, offset + count) as any);
       } else {
         throw new Error('Failed to extract GeoTiffTags');
       }