TIFF 6.0 allows the alpha at any ExtraSamples position, but the decoder
only looked at the first extra sample, and for RGB/CMYK the tiff crate
drops every sample after its colour type. With ExtraSamples [0, 2] the
alpha was silently lost (and gray [0, 2] opened as plain gray).
The alpha is now the first extra sample marked associated (1) or
unassociated (2), wherever it is. When it is not the first extra sample
of an RGB or CMYK image, the crate is asked for every sample (the
photometric is patched to multiband gray, as for WhiteIsZero) and the
colour and alpha samples are picked per chunk; planar files read the
alpha's own plane. Associated alpha in that position is made straight.
Co-authored-by: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
* TIFF: BigTIFF, every IFD and SubIFD, banded parallel decode (FILE-215-8)
Large and multi-page TIFFs now open the way Photoshop opens them, quickly and without a second
full-size buffer, and any directory of the file can be opened on request.
* photocraft-codecs `tiff_ifd`: a bounds-checked directory walker for classic TIFF and BigTIFF
(LONG8 / IFD8, both byte orders). It follows the whole IFD chain and the SubIFD trees (tag
330) with a seen-set, a depth limit and a 10 000-directory cap, and checks every value range
against the file. `tiff_info` lists the pages (size, kind: page / reduced-resolution / mask,
parent, storage); `default_page` is the first full-resolution page of the main chain, so a
leading thumbnail is skipped. `decode_tiff_page`, `tiff_orientation`, `tiff_page_orientation`.
* Banded decode: the `tiff` crate reads the chosen directory through a patched byte view (header
-> that IFD, its next pointer -> 0, WhiteIsZero / palette -> BlackIsZero), so SubIFDs and
cyclic chains decode. The image is allocated once (fallibly, zeroed in parallel) and each
strip or row of tiles, across every plane, is decoded straight into it, in parallel on native
targets, with one capped chunk-sized scratch buffer per worker. New: planar configuration 2
(was an error), palette images (as RGB), 64-bit integers, associated alpha made straight,
non-alpha extra samples dropped. Image data cut off by the end of the file decodes with a
`Truncated` warning. Before the crate sees a file: structural tag values must lie inside it,
the chunk tables must match the geometry (checked in 64 bits; the crate overflowed and
panicked on `(h / rows + 1) * planes`), and a decompression-bomb guard refuses files far too
small for their declared size.
* WhiteIsZero and BigTIFF Orientation keep upstream #746's behaviour (#691, #693) through the
new decode path; regression tests cover both.
* Encode: `EncodeOptions::tiff_bigtiff` writes BigTIFF; without it, BigTIFF is chosen when the
file could pass 4 GiB (and a classic write that overflows 32-bit offsets is redone as BigTIFF).
* photocraft-io: `import_tiff_page(name, bytes, page)`; the TIFF branch of import goes through it.
* Tests: codecs `tiff_pages.rs` on hand-built files (`tests/common/tiffgen.rs`): BigTIFF LE/BE at
8/16/32f, padded tiles and planar strips/tiles, pages and SubIFDs, cycles, the IFD cap,
truncated and past-EOF strips, huge dimensions / counts / tiles, WhiteIsZero, palette, wide
formats, BigTIFF write, and a cut / bit-flip / random-mutation zoo (an ignored long run did
200 000 mutations without a panic); io `tiff_pages.rs`. The `decode_tiff` fuzz target walks
every page. `tiff_bench.rs` (ignored) times a 30 MP decode against the previous path.
* 30 MP RGB (release, 16 threads, same run): Deflate 344 -> 32 ms, LZW 428 -> 43 ms, 16-bit
Deflate 497 -> 46 ms, uncompressed 15 -> 10 ms, 256 px tiles 36 -> 10 ms, planar error -> 12 ms.
* Scorecard FILE-215-8 done; README and roadmap updated.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
* rustfmt the TIFF reader and tests
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: leon <claude.udder842@passmail.net>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>
