fix: support WhiteIsZero

Closes #14

README.md

@@ -1,28 +1,29 @@
 # tiff
 
-  [![NPM version][npm-image]][npm-url]
-  [![build status][travis-image]][travis-url]
-  [![npm download][download-image]][download-url]
+[![NPM version][npm-image]][npm-url]
+[![build status][travis-image]][travis-url]
+[![npm download][download-image]][download-url]
 
 TIFF image decoder written entirely in JavaScript.
 
 ## Installation
 
-```
-$ npm install tiff
+```console
+npm install tiff
 ```
 
 ## Compatibility
 
 ### Platform
 
-This package is written using ES2015 features. It is natively compatible with recent versions of Google Chrome
-and Node.js. You can transpile it with a tool like [babel](https://babeljs.io/) if you need to support more
-JavaScript engines.
+This package is written using ES2015 features. It is natively compatible with
+recent web browsers and Node.js. You can transpile it with a tool like
+[babel](https://babeljs.io/) if you need to support more JavaScript engines.
 
 ### [TIFF standard](./TIFF6.pdf)
 
-The library can currently decode greyscale and RGB images (8, 16 or 32 bits). It does not support any compression algorithm yet.
+The library can currently decode greyscale and RGB images (8, 16 or 32 bits).
+It does not support any compression algorithm yet.
 
 ## API
 
@@ -36,31 +37,33 @@ Each decoded image is stored in an `IFD`.
 
 ##### IFD#data
 
-The `data` property is a Typed Array containing the pixel data. It is a `Uint8Array` for 8bit images, a `Uint16Array` for 16bit images and a `Float32Array` for 32bit images.
+The `data` property is a Typed Array containing the pixel data. It is a
+`Uint8Array` for 8bit images, a `Uint16Array` for 16bit images and a
+`Float32Array` for 32bit images.
 
 ##### Other properties of IFD
 
-* `size` - number of pixels
-* `width` - number of columns
-* `height` - number of rows
-* `bitsPerSample` - bit depth
-* `xResolution`
-* `yResolution`
-* `resolutionUnit`
+- `size` - number of pixels
+- `width` - number of columns
+- `height` - number of rows
+- `bitsPerSample` - bit depth
+- `xResolution`
+- `yResolution`
+- `resolutionUnit`
 
 ### tiff.pageCount(data)
 
 Returns the number of IFDs (pages) in the file.
 
 ### tiff.isMultiPage(data)
 
-Returns true if the file has 2 or more IFDs (pages) and false if it has 1. This is slightly more
-efficient than calling `pageCount()` if all you need to know is whether the file has multiple
-pages or not.
+Returns true if the file has 2 or more IFDs (pages) and false if it has 1.
+This is slightly more efficient than calling `pageCount()` if all you need to
+know is whether the file has multiple pages or not.
 
 ## License
 
-  [MIT](./LICENSE)
+[MIT](./LICENSE)
 
 [npm-image]: https://img.shields.io/npm/v/tiff.svg?style=flat-square
 [npm-url]: https://www.npmjs.com/package/tiff

__tests__/decode.js

@@ -3,9 +3,17 @@ import { join } from 'path';
 
 import { decode } from '../src';
 
-const files = ['grey8.tif', 'grey16.tif', 'color8.tif', 'color16.tif'];
+const files = [
+  'grey8.tif',
+  'grey16.tif',
+  'color8.tif',
+  'color16.tif',
+  'whiteIsZero.tif'
+];
 // const files = ['color8c.tif'];//'grey8.tif', 'grey16.tif', 'color8.tif', 'color16.tif'];
-const contents = files.map((file) => readFileSync(join(__dirname, 'img', file)));
+const contents = files.map((file) =>
+  readFileSync(join(__dirname, 'img', file))
+);
 
 describe('TIFF decoder', () => {
   it('should decode', () => {
@@ -24,7 +32,10 @@ describe('TIFF decoder', () => {
     expect(result[0].data).toBeNull();
   });
   it('should read exif data', () => {
-    const result = decode(contents[0], { onlyFirst: true, ignoreImageData: true });
+    const result = decode(contents[0], {
+      onlyFirst: true,
+      ignoreImageData: true
+    });
     expect(result.exif.map).toEqual({
       ColorSpace: 65535,
       PixelXDimension: 30,

package.json

@@ -34,6 +34,7 @@
     "eslint-config-cheminfo": "^1.18.0",
     "eslint-plugin-import": "^2.14.0",
     "eslint-plugin-jest": "^21.22.0",
+    "esm": "^3.0.82",
     "jest": "^23.6.0",
     "npm-run-all": "^4.1.3",
     "rollup": "^0.65.2"

src/tiffDecoder.js

@@ -62,7 +62,7 @@ export default class TIFFDecoder extends IOBuffer {
     const value = this.readUint16();
     if (value === 0x4949) {
       this.setLittleEndian();
-    } else if (value === 0x4D4D) {
+    } else if (value === 0x4d4d) {
       this.setBigEndian();
     } else {
       throw new Error(`invalid byte order: 0x${value.toString(16)}`);
@@ -145,13 +145,22 @@ export default class TIFFDecoder extends IOBuffer {
       throw unsupported('orientation', orientation);
     }
     switch (ifd.type) {
+      case 0: // WhiteIsZero
       case 1: // BlackIsZero
       case 2: // RGB
         this.readStripData(ifd);
         break;
       default:
         throw unsupported('image type', ifd.type);
     }
+    if (ifd.type === 0) {
+      // WhiteIsZero: we invert the values
+      const bitDepth = validateBitDepth(ifd.bitsPerSample);
+      const maxValue = Math.pow(2, bitDepth) - 1;
+      for (var i = 0; i < ifd.data.length; i++) {
+        ifd.data[i] = maxValue - ifd.data[i];
+      }
+    }
   }
 
   readStripData(ifd) {
@@ -172,15 +181,26 @@ export default class TIFFDecoder extends IOBuffer {
     var remainingPixels = size;
     var pixel = 0;
     for (var i = 0; i < stripOffsets.length; i++) {
-      var stripData = new DataView(this.buffer, stripOffsets[i], stripByteCounts[i]);
+      var stripData = new DataView(
+        this.buffer,
+        stripOffsets[i],
+        stripByteCounts[i]
+      );
 
       // Last strip can be smaller
       var length = remainingPixels > maxPixels ? maxPixels : remainingPixels;
       remainingPixels -= length;
 
       switch (compression) {
         case 1: // No compression
-          pixel = this.fillUncompressed(bitDepth, sampleFormat, data, stripData, pixel, length);
+          pixel = this.fillUncompressed(
+            bitDepth,
+            sampleFormat,
+            data,
+            stripData,
+            pixel,
+            length
+          );
           break;
         case 5: // LZW
           throw unsupported('lzw');
@@ -216,7 +236,10 @@ function getDataArray(size, channels, bitDepth, sampleFormat) {
   } else if (bitDepth === 32 && sampleFormat === 3) {
     return new Float32Array(size * channels);
   } else {
-    throw unsupported('bit depth / sample format', `${bitDepth} / ${sampleFormat}`);
+    throw unsupported(
+      'bit depth / sample format',
+      `${bitDepth} / ${sampleFormat}`
+    );
   }
 }