wmjordan/PDFPatcher · warning · ExifLibException

Error in TIFF data

Error message

Error in TIFF data

What it means

JpgHelper.CreateTagIndex throws ExifLibException('Error in TIFF data') when the 2-byte TIFF magic number immediately after the byte-order marker is not 0x002A. 0x002A is the fixed TIFF signature required by the Exif/TIFF structure; any other value means the TIFF header within the Exif block is invalid.

Source

Thrown at App/Processor/Imaging/JpgHelper.cs:422

				ReadUShort();

				// Next is the Exif data itself. It starts with the ASCII "Exif" followed by 2 zero bytes.
				if (ReadString(4) != "Exif")
					throw new ExifLibException("Exif data not found");

				// 2 zero bytes
				if (ReadUShort() != 0)
					throw new ExifLibException("Malformed Exif data");

				// We're now into the TIFF format
				_tiffHeaderStart = _stream.Position;

				// What byte align will be used for the TIFF part of the document? II for Intel, MM for Motorola
				_isLittleEndian = ReadString(2) == "II";

				// Next 2 bytes are always the same.
				if (ReadUShort() != 0x002A)
					throw new ExifLibException("Error in TIFF data");

				// Get the offset to the IFD (image file directory)
				var ifdOffset = ReadUint();

				// Note that this offset is from the first byte of the TIFF header. Jump to the IFD.
				_stream.Position = ifdOffset + _tiffHeaderStart;

				// Catalogue this first IFD (there will be another IFD)
				_ifd0Catalogue = new Dictionary<ushort, long>();
				CatalogueIFD(ref _ifd0Catalogue);

				// The address to the IFD1 (the thumbnail IFD) is located immediately after the main IFD
				_ifd1Offset = ReadUint();

				// There's more data stored in the subifd, the offset to which is found in tag 0x8769.
				// As with all TIFF offsets, it will be relative to the first byte of the TIFF header.
				uint offset;
				if (!GetTagValue(_ifd0Catalogue, 0x8769, out offset))

View on GitHub (pinned to 4782bbd9ad)

Solutions

1. Catch ExifLibException and treat the Exif block as unreadable, returning empty metadata.
2. Verify the byte-order (II/MM) alignment before reading the magic; a misread offset can also cause this.
3. Repair the JPEG with an Exif-aware tool that can rebuild the TIFF header.
4. Skip and log corrupt files in batch runs.

Example fix

// before
if (ReadUShort() != 0x002A)
  throw new ExifLibException("Error in TIFF data");

// after
if (ReadUShort() != 0x002A) {
  Tracker.TraceMessage(Tracker.Category.Warning, "TIFF 标头无效，跳过 Exif。");
  _ifd0Catalogue = new Dictionary<ushort, long>();
  return;
}

// TIFF magic check is internal; pre-validation requires parsing.
// Wrap the call instead.

try { CreateTagIndex(); }
catch (ExifLibException) { _ifd0Catalogue = new Dictionary<ushort, long>(); }

When it happens

Trigger: A JPEG whose Exif block passes the 'Exif' signature and padding checks but whose embedded TIFF header has a wrong magic number (not 42/0x002A) — indicating corruption of the TIFF portion or a misidentified offset.

Common situations: A corrupt Exif/TIFF header inside an otherwise valid JPEG; byte-level damage to the Exif segment; a malformed Exif block from a non-conformant writer; truncation of the segment.

Related errors

• Malformed Exif data
• Could not find Exif data block
• Exif data not found
• File is not a valid JPEG
• “[]”筛选表达式前缺少节点轴及节点名称标识。

AI-assisted analysis of wmjordan/PDFPatcher@4782bbd9ad (2026-08-13). Data as JSON: /api/errors/27103f456de6d84b. Report an issue: GitHub.