fix: support some malformed images without StripByteCounts

Closes: #38
image-js · Nov 5, 2021 · 56058a9 · 56058a9
1 parent 0cbe52b
commit 56058a9
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Showing 4 changed files with 25 additions and 1 deletion.
diff --git a/img/black.tif b/img/black.tif
diff --git a/src/__tests__/decode.test.ts b/src/__tests__/decode.test.ts
@@ -149,6 +149,14 @@ const files: TiffFile[] = [
     components: 1,
     alpha: false,
   },
+  {
+    name: 'black.tif',
+    width: 9192,
+    height: 2690,
+    bitsPerSample: 16,
+    components: 1,
+    alpha: false,
+  },
 ];
 const cases = files.map(
   (file) => [file.name, file, readImage(file.name)] as const,

diff --git a/src/hacks.ts b/src/hacks.ts
@@ -0,0 +1,15 @@
+import TiffIfd from './tiffIfd';
+
+export function guessStripByteCounts(ifd: TiffIfd): number[] {
+  if (ifd.compression !== 1) {
+    throw new Error(
+      'missing mandatory StripByteCounts field in compressed image',
+    );
+  }
+  const bytesPerStrip =
+    ifd.rowsPerStrip *
+    ifd.width *
+    ifd.samplesPerPixel *
+    (ifd.bitsPerSample / 8);
+  return new Array(ifd.stripOffsets.length).fill(bytesPerStrip);
+}
diff --git a/src/tiffDecoder.ts b/src/tiffDecoder.ts
@@ -1,5 +1,6 @@
 import { IOBuffer } from 'iobuffer';
 
+import { guessStripByteCounts } from './hacks';
 import {
   applyHorizontalDifferencing8Bit,
   applyHorizontalDifferencing16Bit,
@@ -202,7 +203,7 @@ export default class TIFFDecoder extends IOBuffer {
     const rowsPerStrip = ifd.rowsPerStrip;
     const maxPixels = rowsPerStrip * width * ifd.samplesPerPixel;
     const stripOffsets = ifd.stripOffsets;
-    const stripByteCounts = ifd.stripByteCounts;
+    const stripByteCounts = ifd.stripByteCounts || guessStripByteCounts(ifd);
 
     let remainingPixels = size;
     let pixel = 0;