Dylan M. Taylor
603d43da85
PhotoCraft's YCbCr conversion (ReferenceBlackWhite, YCbCrCoefficients, libtiff-compatible green) and FilmCraft's decoding of uncompressed and PackBits subsampled chunky YCbCr images, with PackBits as its own module.
craft-tiff
The TIFF / IFD reader and writer underneath raw decoding (DNG, CR2, NEF, ARW…) and Exif. Moved from
LightCraft's lightcraft-tiff as the first step of shared RAW support (craft-libs#783, #587). It depends
on no other Craft crate.
Features
- Classic TIFF and BigTIFF, little- and big-endian (
II/MM). Also accepts the TIFF-like magic numbers of some raw formats (ORFIIRO/IIRS, RW2IIU) whenParseOptions::accept_raw_magicis set (default). - Every field type: BYTE, ASCII, SHORT, LONG, RATIONAL, SBYTE, UNDEFINED, SSHORT, SLONG, SRATIONAL, FLOAT, DOUBLE, IFD, LONG8, SLONG8, IFD8.
- IFD chain +
SubIFDs(330) + Exif (34665) / GPS (34853) / Interoperability (40965) pointer IFDs, resolved into a tree (Ifd::sub_ifds,exif,gps,interop).Entry::offsetrecords the absolute position of each value (needed for maker notes and embedded blobs). Tiff::parse_with_statusreturns the best-effort tree with a completeness flag for callers that must distinguish a clean absence from an IFD, entry, or pointer that could not be inspected.parse_ifd_at(data, offset, order, base, bigtiff, opts)parses an IFD whose offsets are relative to an arbitrary base;makernote::parse_makernoteknows the header / byte-order / offset-base conventions of Canon, Nikon (types 1 and 3), Sony, Fujifilm, Olympus (old and new), Panasonic and Pentax notes.image::ImageInfo— width/height, bits, samples, compression, photometric, planar config, predictor, sample format and the strip or tile chunk list (chunks(),chunk_bytes()); missing byte counts are inferred.directory_entries,entry_span,ParseOptions::budget_foranddecode_valueare the reader's own rules (directory layout and entry limit, which entries it reads, its value budget, value decoding), for callers that must select entries exactly asparse_ifd_atwould without decoding the whole directory (e.g. a raw decoder's SonySR2Privatelookup).TiffWriterwrites IFD chains with strips or tiles,SubIFDsand pointer IFDs, in either byte order, classic or BigTIFF;writer::rational/srationalapproximate floats as rationals.
Robustness
The reader never panics on malformed input (proptests feed random and mutated files): offsets are
bounds-checked; out-of-range or unknown-type entries are skipped; IFD loops are detected; IFD count,
nesting depth and entries per IFD are limited; at most 65,536 directory entry slots
(ParseOptions::max_entries_total) are accepted across the main IFD chain and all child IFDs, even when tables
overlap at distinct offsets, and an IFD past that bound ends the chain or is skipped like any other bad IFD after
the first; a next-IFD pointer is followed only when every declared entry was read, with the counts compared as
64-bit numbers (a BigTIFF declaring 4,294,967,297 entries but holding one can't pass for a whole directory on a
32-bit target); the total bytes of decoded values are capped at
8 × input + 1 MiB so a file cannot make us allocate far more than its own size. parse_with_status reports
truncated tables, skipped values, unresolved pointers and incomplete IFD chains without changing the parser's
best-effort tree.
Sources
Public specifications only: TIFF 6.0 (Adobe, 1992), the TIFF 6.0 supplements (IFD type, SubIFDs), the BigTIFF format description (AWare Systems), Adobe DNG Specification 1.7 (tag numbers), CIPA DC-008 Exif 2.32, and the ExifTool tag-name documentation (maker-note header conventions, prose only). No third-party code was consulted.