FITS BLANK — Undefined Integer Pixels (.fits)
Integer FITS images mark undefined pixels with the BLANK keyword, and BLANK is compared against the stored value before BZERO and BSCALE are applied. Scale first and the four undefined pixels turn into a perfectly plausible zero, which is the ordering bug this file exists to expose.
| Pixel | Stored | After BZERO | Meaning |
|---|---|---|---|
| [0,0] | -32768 | 0 | BLANK — undefined, must be masked |
| [0,1] | -32768 | 0 | BLANK — undefined |
| [0,2] | -32768 | 0 | BLANK — undefined |
| [7,7] | -32768 | 0 | BLANK — undefined |
| others | signed 16-bit | 0 to 65535 | real ADU values |
Specifications
- Bitpix
- 16
- Blank
- -32768
- Blank Pixels
- 4
- Bzero
- 32768
- Trap
- BLANK is compared to the STORED value, before BZERO/BSCALE
Testing contract
Expected to pass- Scenario
- Mask pixels equal to BLANK and only then apply BZERO and BSCALE, and count how many pixels were masked.
- Expected result
- Exactly four pixels mask out; applying the scaling first leaves those pixels reading 0 ADU and the mask empty.
What is a .fits file?
FITS (.fits, Flexible Image Transport System) is the standard binary format in astronomy. It pairs human-readable 80-character header cards (in 2880-byte blocks) with binary image or table data, storing pixel arrays, coordinates, and instrument metadata. It has been the astronomical archive format for decades.
How to use this file
Use an example .fits file to test FITS readers (astropy, CFITSIO, DS9), header-card parsing, and image or table extraction, or to verify block-alignment handling.
How to use this file for testing
“FITS BLANK — Undefined Integer Pixels (.fits)” is a deterministic Novus Examples fixture for Scientific data, Serialization testing, Error handling. Citation catalogs (BibTeX, RIS), chemistry structures (MDL Molfile, PDB), and gridded binary data (NetCDF, FITS) — for testing reference managers, molecule viewers, and scientific-data loaders.
Documented properties for this file: FITS · 5,760 bytes. Compare results against paired or grouped companions on this page when present (clean↔damaged, searchable↔scanned, or format twins) so scores stay reproducible across runs.
Download the file once, keep the path stable in CI or local scripts, and treat the spec table as the contract: dimensions, seeds, field lists, and roles are intentional. Corrupt or invalid samples are labelled as such — expect parsers to fail loudly rather than silently accept them.
Scientific fixtures are small, valid, and fully synthetic — no real organism, patient, sample, or observation. Point your parser or loader at the file and check it reads the documented records, variables, or headers; binary formats ship a readable twin or metadata listing for comparison.
Related files
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- h5HDF5 Degenerate Shapes — Scalar, Zero-Length and Null (.h5)Five degenerate but entirely legal datasets — a rank-0 scalar, a zero-length vector, a (0, 5) array, a single-element vector and a NULL dataspace — plus an empty group. None of them is corrupt, and a reader that reports them as errors is the thing being tested.
- h5HDF5 Hard, Soft and Dangling Links (.h5)One array reachable under four names: itself, a hard link sharing its object address, a soft link resolved at access time, and a soft link pointing nowhere. A walker that counts names instead of object addresses reports four arrays and then crashes on the dangling one.
- h5HDF5 Numeric dtype Zoo — Every Width at Its Limits (.h5)Twelve datasets, one per numeric HDF5 type, each holding the extreme values of that type including the uint64 and int64 limits that do not survive a trip through a double. It is the fixture that exposes a reader which widens everything to float64 on the way in.
- ncNetCDF _FillValue, missing_value and NaN Together (.nc)One variable that hides absent data three different ways at once: two _FillValue cells, one legacy missing_value cell and one raw NaN, with valid_min and valid_max also declared. Averaging the raw array without honouring all three gives roughly -60 K instead of a real mean.
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