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Dylan M. Taylor 219f63f64c Add craft-xcf: GIMP XCF reader from PhotoCraft (#960 )

* Add craft-xcf: GIMP XCF reader from PhotoCraft

The format half of PhotoCraft's XCF import (crates/io/src/xcf.rs at abeb16c96): the header,
precisions, property lists with their length repairs, parasites, layer structures and item
paths, channels, and the uncompressed, RLE and zlib tiles. The mapping onto a document (blend
modes, surfaces, profiles, warnings) stays in the app.

* craft-xcf: an RLE run of zero length is an error

A long run (op 127 or 128) with a 16-bit length of 0 consumed input without producing output,
so a tile of them was work the pixel budget never charged.

Ported from storytold/photocraft#11138.

* craft-xcf: channel names are charged to the metadata budget

Layer names already were. Many channel pointers to one channel with a large name made a copy
per read, multiplying a small file into gigabytes of retained names.

Ported from storytold/photocraft#11138.

2026-11-11 19:25:01 -05:00

src

Add craft-xcf: GIMP XCF reader from PhotoCraft (#960 )

2026-11-11 19:25:01 -05:00

Cargo.toml

Add craft-xcf: GIMP XCF reader from PhotoCraft (#960 )

2026-11-11 19:25:01 -05:00

README.md

Add craft-xcf: GIMP XCF reader from PhotoCraft (#960 )

2026-11-11 19:25:01 -05:00

README.md

craft-xcf

GIMP XCF images (.xcf, .xcf.gz), read. Written from the public specification (https://developer.gimp.org/core/standards/xcf/, versions 0 to 26) and from files GIMP 3.2 writes; no GIMP code is used.

is_xcf, is_gzipped_xcf, gunzip: recognise a file and inflate a compressed one.
Xcf::parse: the header, the image properties and every layer structure, as an Image: version, canvas, base type, Precision, Compression, colormap, resolution, guides, the ICC profile and comment parasites, the path count, and each Layer with its properties as GIMP wrote them (mode, opacity, offsets, locks, colour tag, composite mode and spaces, group flag, item path, text / vector / link flags, effect count). No pixel is decoded.
Xcf::layer_pixels, Xcf::layer_mask, Xcf::channel: one drawable's pixels as normalised f32 samples (Pixels), from uncompressed, RLE or zlib tiles at every precision (8, 16 and 32-bit integer; 16, 32 and 64-bit float). Indexed pixels are expanded through the colormap. Each call takes its samples from a byte budget the caller owns, and a keep_going callback.
Image::tree: the layers arranged by their item paths, with the ones whose path leads nowhere or nests too deep reported.

The reader repairs what GIMP writes wrongly: the length words of PROP_COLORMAP, PROP_USER_UNIT and PROP_LINK_LAYER are measured, not trusted.

Layer modes, colour tags and composite settings stay numbers: what they mean to an application is not decided here. Paths, layer effects and text or vector layer data are not read (their presence is reported). There is no writer.

Limits

Limit	Value
Canvas or drawable side	300,000 px (`MAX_SIDE`)
Canvas area	1 GiB at 16 bytes per pixel (`MAX_PIXEL_BYTES`)
Decoded pixels	the caller's budget, charged 4 bytes a sample before allocation
Layers	8192 (`MAX_LAYERS`); channels 1024 (`MAX_CHANNELS`)
Layer effects on one layer	1024
Properties in one list	4096; a payload 64 MiB (`MAX_PAYLOAD`)
A string	1 MiB (`MAX_STRING`)
Copied layer and channel names and item paths	32 MiB in all (`MAX_METADATA_BYTES`)
Group nesting in `Image::tree`	64 (`MAX_DEPTH`)
A gzipped file, inflated	1 GiB (`MAX_INFLATED`)