feat: expose gdal's NO_DATA as a getter on the image (#1230)

blacha · Nov 26, 2023 · fc21a30 · fc21a30
1 parent 44757e5
commit fc21a30
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Showing 2 changed files with 16 additions and 0 deletions.
diff --git a/packages/core/src/__test__/cog.read.test.ts b/packages/core/src/__test__/cog.read.test.ts
@@ -86,6 +86,9 @@ describe('CogRead', () => {
     assert.equal(im.value(TiffTag.SampleFormat), SampleFormat.Float);
     assert.equal(im.value(TiffTag.Photometric), Photometric.MinIsBlack);
 
+    assert.equal(im.value(TiffTag.GdalNoData), '-9999');
+    assert.equal(im.noData, -9999);
+
     assert.equal(im.tagsGeo.get(TiffTagGeo.GTCitationGeoKey), 'NZGD2000 / New Zealand Transverse Mercator 2000');
     assert.equal(im.tagsGeo.get(TiffTagGeo.GeodeticCitationGeoKey), 'NZGD2000');
     assert.deepEqual(await im.fetch(TiffTag.StripByteCounts), [8064, 8064, 8064, 8064, 8064, 8064, 8064, 5040]);

diff --git a/packages/core/src/tiff.image.ts b/packages/core/src/tiff.image.ts
@@ -162,6 +162,19 @@ export class TiffImage {
     return this.tagsGeo.get(tag) as TiffTagGeoType[T];
   }
 
+  /**
+   * Load and parse the GDAL_NODATA Tifftag
+   *
+   * @throws if the tag is not loaded
+   * @returns null if the tag does not exist
+   */
+  get noData(): number | null {
+    const tag = this.tags.get(TiffTag.GdalNoData);
+    if (tag == null) return null;
+    if (tag.value) return Number(tag.value);
+    throw new Error('GdalNoData tag is not loaded');
+  }
+
   /**
    * Load and unpack the GeoKeyDirectory
    *