missing DOUBLE case metadata properties on geotiffwriter

[jo-chemla]

Context is I'm just trying to export geotiffs with EPSG:4326 CRS, and then importing/exporting the result which yields to this error.

I'm trying to read an input geotiff via fromBlob, edit its raster values, and export via writeArrayBuffer but exporting yields the below errors:

[geotiff.js] couldn't get TIFFTagLocation for GeogSemiMajorAxisGeoKey [geotiffwriter.js:469:17](http://localhost:5173/node_modules/geotiff/dist-module/geotiffwriter.js)
[geotiff.js] couldn't get TIFFTagLocation for GeogInvFlatteningGeoKey

These errors redirect to these lines:

geotiff.js/src/geotiffwriter.js

Lines 460 to 470 in c0c5f76

	if (fieldTagTypes[KeyID] === 'SHORT') {
	Count = 1;
	TIFFTagLocation = 0;
	valueOffset = metadata[geoKey];
	} else if (geoKey === 'GeogCitationGeoKey') {
	Count = metadata.GeoAsciiParams.length;
	TIFFTagLocation = Number(name2code.GeoAsciiParams);
	valueOffset = 0;
	} else {
	console.log(`[geotiff.js] couldn't get TIFFTagLocation for ${geoKey}`);
	}

Could it be that GeogSemiMajorAxisGeoKey and GeogInvFlatteningGeoKey are DOUBLE according to the geotiff spec and

• mappings should be added in file globals.js to the fieldTagTypes object, where 2057 and 2059 should be DOUBLE?
• and the case fieldTagTypes[KeyID] === 'DOUBLE' should be handled properly in the GeoKeyDirectory object? Is it simply a matter of Count = 2 in the DOUBLE case?

For reference, here is an extract of the read/write code, parsing geoMetadata on read and exploding it into the metadata object passed to writeArrayBuffer.

  const tiff = await fromBlob(file);
  const image = await tiff.getImage();
  const rasters = await image.readRasters({ interleave: true });

   const geoMetadata = {
      geoKeys: image.getGeoKeys(),
      fileDirectory: image.fileDirectory,
    }

  const { ModelPixelScale, ModelTiepoint, ImageWidth: width, ImageLength: height } = geoMetadata.fileDirectory;
  const metadata = {
    // GeographicTypeGeoKey: geoMetadata.geoKeys.GeographicTypeGeoKey,
    width,
    height,
    ModelPixelScale,
    ModelTiepoint,
    // ...geoMetadata.fileDirectory
    ...(geoMetadata.geoKeys), 
    // couldn't get TIFFTagLocation for GeogSemiMajorAxisGeoKey, GeogInvFlatteningGeoKey
  };
  const metadata_ = JSON.parse(JSON.stringify(metadata)); // deep clone copy
  const arrayBuffer = await writeArrayBuffer(raster, metadata_);

[DanielJDufour]

Hi, @jo-chemla . Thank you for catching this issue and the suggested fix! Could you create a PR resolving this issue? If you can include a test in your PR that tests this new change that would be great too!

[jo-chemla]

Thanks for getting back so fast. I gave it a try here #477 !

Copy-pasting below the PR message:
This GeoTIFF spec by maptools was a very important resource to understand these ascii and double tags and how they relate to GeoKeyDirectory
Note I have added both

• handling of DOUBLE GeoKeys
• but also extended ASCII Geokeys so not only GeogCitationGeoKey gets parsed

Also, I later decided to build the offsets object when adding type-filtered keys to the GeoDoubleParams, GeoAsciiParams structures, to avoid recomputing them afterwards when adding to GeoKeyDirectory.

EDIT: also managed to import test-data - on a windows machine, had to rework some wget/unzip and gdal commands - and added a test to geotiffwriter spec, only for the case I added of DOUBLE/ASCII parsing.