aiongg
035d4d5dcb
docs/gaps.md, docs/parity-checklist.md, docs/whats-new.md: both sides kept; the PR's sentences added to main's rows and entries. docs/xmp-interop.md: capture-time paragraph combines both sides. The PR's test file crates/engine/src/tests_import.rs landed in crates/engine/src/tests/import.rs (moved on main).
lightcraft-meta (L1)
Photo metadata: EXIF, XMP (read + write), IPTC-IIM, and the containers that carry them.
API
| Function | Purpose |
|---|---|
read_exif(&[u8]) -> Metadata |
TIFF-structured Exif block (whole TIFF/DNG/raw file, or JPEG APP1 payload with/without Exif\0\0). try_read_exif reports header errors. |
from_tiff(&Tiff) -> Metadata |
Same, from an already parsed stream (used by lightcraft-raw). |
embedded(&[u8]) -> Embedded |
Sniffs JPEG / PNG / WebP / TIFF / PSD / PSB and returns the Exif, XMP (+ extended XMP), ICC and IPTC blocks. PSD/PSB EXIF resource 1058 and XMP resource 1060 are read from the bounded image-resource section without decoding pixels. jpeg_segments, png_chunks, webp_chunks are the per-container walkers. |
parse_xmp(&str) -> Result<XmpData> |
Metadata + the opaque lc:settings JSON + every property (prefix:name, structs flattened as a:b/c:d). |
write_xmp(&Metadata, Option<&str>) -> String |
Complete <?xpacket?> packet; the second argument is LightCraft's full develop settings JSON. |
parse_iptc(&[u8]) -> Metadata |
IIM record 2: title (2:5), keywords (2:25), by-line (2:80), copyright (2:116), caption (2:120), date/time created (2:55/2:60). |
extract(&[u8]) -> Metadata |
Everything for a whole file. Precedence: EXIF → IPTC fills gaps → XMP overrides user fields (rating, label, title, caption, artist, copyright, keywords, GPS) and fills the rest. |
try_extract(&[u8]) -> Result<Metadata, ExtractError> |
Like extract, but reports malformed PSD/PSB headers, image-resource sections, or embedded EXIF/XMP structure (including duplicate EXIF/XMP resources) so callers can fail closed when location absence cannot be established. Other formats remain best-effort. |
Metadata carries camera (make, model, serial, software), lens (make, model, serial, specification), capture
(date-time with UTC offset and milliseconds, exposure time, f-number, ISO incl. extended ISO, focal length and
35 mm equivalent, flash, exposure bias, program, metering, white balance), orientation, GPS, dimensions and the
user fields (artist, copyright, title, caption, keywords, hierarchical keywords, rating −1…5, colour label).
EXIF capture-time candidates are tried in order: DateTimeOriginal, DateTimeDigitized, then IFD0 DateTime. A clock with more than three colon-separated components is rejected as a whole, allowing the next valid candidate or XMP fallback to supply the capture time. The original tag remains available in All Metadata.
XMP namespaces
Written: dc, xmp, photoshop, exif, exifEX, tiff, lr (hierarchicalSubject) and ours,
lc = http://ns.lightcraft.app/lc/1.0/ (lc:settings, an opaque JSON string). Reading canonicalises
prefixes by namespace URI, handles attribute and element forms, rdf:Seq/Bag/Alt (x-default first),
rdf:parseType="Resource" and nested-description structs, predefined and numeric entities. Nesting depth
and node count are limited.
An explicitly foreign namespace using a recognized prefix (for example lc or xmp) cannot supply
recognized properties. Its keys use Q{hex-encoded namespace URI}local in properties and values;
hex encoding keeps / reserved for struct paths. Other unknown prefixes keep their existing QName keys.
Merging preserves the original foreign XML rather than writing these opaque keys into the packet.
The parser and merge scanner each cap generated opaque names at 8 MiB per packet, returning TooComplex
if repeated use of a long namespace URI would exceed that budget.
Robustness
No panics on malformed input: proptests feed random bytes to every container walker and random text to the XMP parser; truncation tests cut a sample JPEG at every byte and exercise truncated PSD/PSB headers and image-resource records with hostile declared lengths. PSD/PSB XMP resources require valid UTF-8; trailing NUL padding is trimmed after validation.
ISO capture-time parsing requires a complete clock and consumes every clock and fractional-second character. Invalid
XMP capture-time values remain available in the raw property map but are not projected into Metadata; a later valid
capture-time property can still supply the metadata value. Invalid GPX point times are treated as untimed.
Sources
CIPA DC-008 (Exif 2.32), TIFF 6.0, Adobe DNG 1.7 (tag numbers), ISO 16684-1 / Adobe XMP Specification
Parts 1–3 (packet, RDF serialisation, standard schemas, JPEG extended XMP), IPTC-IIM 4.2 and the IPTC Photo
Metadata Standard, ITU-T T.81 (JPEG markers), ICC.1 (APP2 embedding), PNG Specification 3rd ed. (eXIf,
iTXt), the WebP RIFF container specification, Adobe Photoshop File Format Specification (image resource
blocks). XML parsing: quick-xml (MIT). No third-party metadata code was consulted.