`embedded_preview_srgb` (the loupe stand-in and the grid thumbnail of an unedited raw) decoded the
largest embedded JPEG whatever the size asked for: a 512 px thumbnail of a Sony A7R VI ARW decoded
its 9984 x 6656 JPEG (5.6 MB) although the file holds a 1616 x 1080 one (0.3 MB).
`lightcraft_raw::embedded_preview_covering(bytes, min_edge)` returns the smallest of a TIFF-based
raw's JPEGs whose long edge is at least `min_edge` and that is a copy of the largest one: aspect
ratio within 1 % (not a letterboxed thumbnail of another shape) and the same number of components
(not the grey semantic masks of an iPhone ProRAW DNG); else the largest, as `embedded_preview`.
The colour-space handling stays in `decode_raw_preview` (a `covering` argument); an unsupported
raw's editing source and the camera-look fit keep the largest JPEG, so a source never depends on
its size level.
On 120 raws of every make in the corpus at 256 / 512 / 1600 px: wherever the largest JPEG is still
chosen the output is identical byte for byte; where a smaller one is (Sony, Nikon, Panasonic,
Adobe DNG) orientation matches, the size is equal or 1-2 px off, mean difference <= 4.7 / 255.
- Rebased onto #1020: its plan route (`preview_window` -> `planned_preview`) now takes the box size and picks
with `embedded_preview_covering` too, so a TIFF raw read through the sparse plan gets the whole file's JPEG.
Co-Authored-By: Claude <[email protected]>
The header-only path added in #755 answers for a Fuji RAF, whose preview pointer sits in the first
bytes. A Canon CR3 keeps its preview in a JPEG track, and a TIFF raw (CR2, ARW, DNG, RW2, 3FR …) can
keep its preview tag in an IFD the prefix cuts short: both fell back to `std::fs::read` of the whole
file — tens of megabytes for a JPEG of a few, on the format of the largest bucket in gaps.md (Canon,
33 % of photographers).
`preview_window` now asks `lightcraft_raw::sparse::preview_plan` — the module #961 added for the
import path, which had no production caller — which ranges `embedded_preview` reads, and reads
exactly those: `planned_preview` fills a buffer of the file's length, reads the ranges the plan names
and asks again until it says `Ready`. The buffer is the file's length, which the memory gate counted
already, and its untouched pages stay zero, so what this path costs is the bytes read — on macOS a
freed buffer of that size may sit in the allocator's cache rather than go back to the OS (measured on
a 38k-photo import, #832). The loop gives up past 60 % of the file, the bound step 2's partial read
uses, and a plan that does not fit, a file past 1 GiB or a window that does not decode all end in the
whole-file fallback.
The quick path hands the JPEG to the decoder alone, so two container facts the whole-file path applies
have to be visible in the bytes it is handed, or the file declines and the whole file keeps the
preview:
- a preview colour space of Adobe RGB (`decode_raw_preview` applies it; a JPEG-only decode has the
JPEG's own space, else sRGB). A container that says sRGB does not decline — that is what the decode
assumes anyway, and declining it took the fast path away from a real Sony ARW;
- the file's own EXIF orientation, when the preview JPEG carries none of its own: the plan's header is
a bounded 64 KiB (the header route grows its prefix to the preview's declared extent instead), and
an orientation tag it cannot see would show the preview unrotated.
Measured over the whole CC0 corpus (111 raws): 52 files take this route, reading a median 7.8 % of
their bytes (0.9-27.7 %) — RW2 3.3 %, Leica RWL 4.1 %, ARW 7.5 %, CR3 8.4 %, DNG 9.7 %, CR2 14.3 % —
while the 21 RAFs stay on the header route (median 4.5 %). The other 38 read whole: NEF, NRW, ORF, PEF
and SRW because the planner does not describe them (an SRW plans to the whole file, which the 60 %
budget then declines), plus the ARWs, CR2s, CR3s and DNGs that declare Adobe RGB or whose plan wants
more than that budget — the bytes they read are the ones the plan would have read anyway. Across all
111 files the plan handed on the same preview as the whole file, with the skipped bytes zeroed and
again 0xFF. `LIGHTCRAFT_PROFILE=1` prints
[profile] preview …/arw-sony-a7rm4a-compressed.arw: read 688128 of 61832192 bytes (plan, window 483441)
Tests: a synthetic TIFF/DNG whose preview only its tags locate (identical pixels to the whole-file
path, the CFA strip unread), the same structure without the tag that makes it a raw, a file whose
orientation only the whole file shows, and a file that states Adobe RGB against one that states sRGB;
the opt-in real-file test reports which path answered.
Co-Authored-By: DeepSeek V3.2 <[email protected]>
A grid thumbnail and a loupe preview of an unedited raw show the camera's embedded JPEG, which
sits near the start of the file — for a 24 MP Fuji RAF, 5.6 MB of a 56 MB file (measured:
DSCF9492.RAF). The loader read the file whole and threw the sensor data away, so every preview
paid for 50 MB nobody looked at. On a local disk that is merely wasteful; on a network share,
where photographers keep libraries, it is the wait: the same preview took 10 s over a GVFS/SMB
Wi-Fi share against 0.96 s after this change.
- `lightcraft_raw::bounded_preview(bytes)` locates the preview from the header alone and reports
its byte range; `embedded_preview_from_range` extracts it, byte for byte what `embedded_preview`
returns for the whole file (the pointer is read from the RAF header's fixed u32s at 84/88).
- `engine::files::preview_window` reads a 4 KiB prefix, then — because the container reader clamps
a slice to the buffer it was given, so a short prefix reports a plausible but truncated 3948
bytes — re-reads exactly the extent the header declares, and takes the window out of the prefix
rather than reading those bytes twice. `LIGHTCRAFT_PROFILE=1` prints what each preview cost.
- Formats whose preview only the whole file reveals (CR3 boxes, TIFF pointer tags past the prefix,
CRW/MRW/X3F scans), a lying pointer, a short read and a file that changes underneath us all fall
back to the whole-file path: a damaged header never costs the user their preview.
- Tests: the header range matches `embedded_preview` byte for byte, with a clamped prefix, a padded
extent, a late pointer, a lying pointer and a non-JPEG window covered; on a synthetic RAF with a
200 KB tail the quick path and the whole-file path produce identical pixels and the read stays
under half the file; `crates/engine/tests/preview_read.rs` (opt-in, `#[ignore]`) measures a real
file on a share. No raw fixture is committed.
- `docs/raw-preview-reads.md` records the mechanism and the numbers.
Co-Authored-By: DeepSeek V3.2 <[email protected]>
Recover the unpublished denoise work against current upstream. Preserve later opt-in model setup, shared Rust HTTPS downloads, pending-photo resume and an Amount-independent switch. Keep original RAWs unchanged and share the current color finish between ordinary and denoised sources.
Bound public tiling inputs, refuse corrupt-cache exports, and retain synthetic/real-model coverage. Include two Windows path spelling fixes in existing tests. No model weights, face code, media or Tract runtime are included.
Validation: cargo xtask ci (all seven gates); installed RawNIND CPU/GPU agreement 1.38e-6; native CPU preview/export on a public 24 MP Sony RAW, unchanged original SHA-256.
Co-authored-by: Codex <[email protected]>
Co-authored-by: Claude Sonnet 5.5 <[email protected]>
Generated with Codex.
