Address review comments: default to Float64

Addressing Daniel's review comments on PR #366, I've followed his advice
to change the default writing to use Float64Array, rather than
Uint8Array (which users can still provide manually).

Author: TheMrCam

src/geotiffwriter.js

@@ -257,7 +257,8 @@ const encodeImage = (values, width, height, metadata) => {
   const dataType = values.constructor.name;
   const TypedArray = typeMap[dataType];
 
-  let elementSize = 4;
+  // default for Float64
+  let elementSize = 8;
   if (TypedArray) {
     elementSize = TypedArray.BYTES_PER_ELEMENT;
   }
@@ -277,7 +278,9 @@ const encodeImage = (values, width, height, metadata) => {
     const buffer = new ArrayBuffer(elementSize);
     const view = new DataView(buffer);
 
-    if (dataType === 'Float32Array') {
+    if (dataType === 'Float64Array') {
+      view.setFloat64(0, value, false);
+    } else if (dataType === 'Float32Array') {
       view.setFloat32(0, value, false);
     } else if (dataType === 'Uint32Array') {
       view.setUint32(0, value, false);
@@ -388,8 +391,8 @@ export function writeGeotiff(data, metadata) {
   if (!metadata.StripByteCounts) {
     // we are only writing one strip
 
-    // default for Uint8
-    let elementSize = 1;
+    // default for Float64
+    let elementSize = 8;
 
     if (ArrayBuffer.isView(flattenedValues)) {
       elementSize = flattenedValues.BYTES_PER_ELEMENT;

src/utils.js

@@ -188,6 +188,7 @@ export function isTypedUintArray(input) {
 }
 
 export const typeMap = {
+  Float64Array,
   Float32Array,
   Uint32Array,
   Uint16Array,

test/geotiff.spec.js

@@ -126,6 +126,7 @@ describe('writeTypedArrays', () => {
     new Uint16Array(generateTestDataArray(0, 65535, dataLength, true)),
     new Uint32Array(generateTestDataArray(0, 4294967295, dataLength, true)),
     new Float32Array(generateTestDataArray(-3.4e+38, 3.4e+38, dataLength, false)),
+    new Float64Array(generateTestDataArray(Number.MIN_VALUE, Number.MAX_VALUE, dataLength, false)),
   ];
 
   const height = Math.sqrt(dataLength);
@@ -141,7 +142,7 @@ describe('writeTypedArrays', () => {
         width,
       };
 
-      const newGeoTiffAsBinaryData = await writeArrayBuffer((originalValues), metadata);
+      const newGeoTiffAsBinaryData = await writeArrayBuffer(originalValues, metadata);
       const newGeoTiff = await fromArrayBuffer(newGeoTiffAsBinaryData);
       const image = await newGeoTiff.getImage();
       const newValues = await image.readRasters();