hesela.devTIFF image file directory
A TIFF image file directory is a set of tagged entries describing an image and locating its associated data within a TIFF file.
Classic TIFF links the header to the first IFD and each main-chain IFD to its successor; zero terminates that chain. Baseline readers may ignore images after the first, so format support alone does not promise complete image enumeration. [1]
In Hesela's 14 controlled LibTIFF 4.5.1 fixtures, one changed pointer byte ended traversal after A while all original pixels for A-B-C survived. Known-offset selection still decoded B. Reordering to A-C-B preserved count and unordered pixel hashes but failed the independently fixed ordered requirement. These are synthetic native observations, not failure rates. [2]
TIFFReadDirectory returns zero for errors as well as end-of-chain. Preserve diagnostics and terminal state. Selecting an independently known directory offset is different from discovering an orphaned image. [3] [4]
Main-chain traversal does not cover every SubIFD relationship. OME-TIFF TiffData can map physical IFDs to logical planes in another order; pyramid levels intentionally stay outside the main chain and TiffData. No OME or SubIFD reader was tested here. [5] [6]
These fixtures are recovery controls, not TIFF 6.0 conformance examples: even the original shares resolution-value offsets across IFDs, and the alias control additionally shares a pixel-strip pointer. Section 7 warns against duplicate pointers and does not require readers or editors to detect them. Successful decoding alone does not establish conformance. [1]
For scientific reuse, pixel identity alone does not establish preservation of the acquisition metadata. Linkert et al.'s 2010 review recommends retaining metadata with image data and through analysis; this supports a separate metadata-preservation requirement, not a TIFF recovery-rate estimate. [8]
Relations
- related
- Backup verification, Restore test, Checksum
Limitations
- No BigTIFF, codec, OME, SubIFD or hardware-fault experiment. Every modified fixture changes the whole-file digest; no hash-collision or library-defect claim.
Citations
- TIFF Revision 6.0 (1992), sections 2 and 7: IFD structure and reader scope
- Hesela: native TIFF reachability, order and identity observations
- LibTIFF TIFFReadDirectory: return values and diagnostics
- LibTIFF TIFFSetDirectory and TIFFSetSubDirectory: ordinal versus offset
- LibTIFF: main-chain and SubIFD traversal
- OME-TIFF 6.2.2: TiffData and sub-resolution storage
- Linkert et al. (2010), Metadata matters: access to image data in the real world; microscopy file formats and Box 1
Further reading
Sources & caveats
- TIFF specification and official library/OME documentation; controlled native observations on one Linux LibTIFF 4.5.1 build. The upstream tag is not asserted identical to the patched distribution binary.