Brandon ThomasandClaude Opus 5.5
882a059fac
Saving (Cmd+S or auto-write) now merges LightCraft's properties into an existing sidecar (lightcraft_meta::merge_xmp): owned properties (rating, label, dc/IPTC/rights fields, lc:*) are replaced or removed, capture time and GPS only when LightCraft has a value; everything else (crs:, xmpMM:History, unknown namespaces, packet wrapper) is kept byte for byte. The result is re-parsed and checked before it is written (temp + fsync + rename). A sidecar that isn't valid XMP is copied to .xmp.bak-<time> (never overwriting) before it is replaced; one that can't be read at all is left alone and the save fails. Shared stems: when several catalogued files map to one stem sidecar (IMG.CR3 + IMG.JPG), it belongs to the raw (else the first by name) and the others write and read <file>.xmp. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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 and returns the Exif, XMP (+ extended XMP), ICC and IPTC blocks. 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. |
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).
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.
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.
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.