doc: tag access via .value() and .valueGeo() (#1231)

README.md

@@ -23,6 +23,11 @@ const cog = await Tiff.create(source);
 const img = cog.images[0];
 if (img.isTiled()) throw new Error('Tiff is not tiled');
 const tile = await img.getTile(2, 2); // Fetch a tile from a tiff x:2, y:2
+
+// Tiff tags can be access too
+img.value(TiffTag.GdalNoData); // "-9999"
+// or tag metadata can be accessed
+img.tags.get(TiffTag.GdalNoData);
 ```
 
 ## Command Line Interface

packages/core/README.md

@@ -36,8 +36,27 @@ if (img.isTiled()) {
 const origin = img.origin;
 /** Bounding box of the tiff */
 const bbox = img.bbox;
+
+// Tiff tags can be accessed via some helpers
+const noData = img.noData; // -9999
+const noDataTag = img.tags.get(TiffTag.GdalNoData) // Tag information
+const noDataValue = img.value(TiffTag.GdalNoData) // "-9999" (tag is stored as a string)
 ```
 
+### Tags
+
+Some tags have exported constants to make them easier to work with
+
+```typescript
+const photometric = img.value(TiffTag.Photometric)
+
+if( photometric == Photometric.Rgb) { 
+  // Tiff is a RGB photometric tiff
+}
+```
+
+For a full list see [./src/index.ts](./src/index.ts)
+
 
 More examples can bee seen
 

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

@@ -89,8 +89,8 @@ describe('CogRead', () => {
     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.equal(im.valueGeo(TiffTagGeo.GTCitationGeoKey), 'NZGD2000 / New Zealand Transverse Mercator 2000');
+    assert.equal(im.valueGeo(TiffTagGeo.GeodeticCitationGeoKey), 'NZGD2000');
     assert.deepEqual(await im.fetch(TiffTag.StripByteCounts), [8064, 8064, 8064, 8064, 8064, 8064, 8064, 5040]);
   });
 
@@ -125,6 +125,6 @@ describe('CogRead', () => {
       'ProjLinearUnitsGeoKey',
     ]);
 
-    assert.deepEqual(im.tagsGeo.get(TiffTagGeo.GeogTOWGS84GeoKey), [0, 0, 0, 0, 0, 0, 0]);
+    assert.deepEqual(im.valueGeo(TiffTagGeo.GeogTOWGS84GeoKey), [0, 0, 0, 0, 0, 0, 0]);
   });
 });

packages/core/src/tiff.image.ts

@@ -134,7 +134,7 @@ export class TiffImage {
    *
    * @example
    * ```typescript
-   * img.fetch(TiffTag.ImageWidth) // 512 (px)
+   * await img.fetch(TiffTag.ImageWidth) // 512 (px)
    * ```
    *
    * @param tag tag to fetch