xisf-rs

License

An unaffiliated implementation of Pleiades Astrophoto's open-source Extensible Image Serialization Format (XISF) file format, the native image format for their flagship editing software PixInsight. Aims for 100% support for spec version 1.0, as opposed to implementations such as libXISF or Pleiades Astrophoto's own PixInsight Class Libraries, which are written with 2D images in mind. Currently under rapid development, but all changes to the public API will be accompanied with a version update following Cargo's SemVer guidelines before being pushed to crates.io.

Feature Comparison

| xisf-rs | libXISF | PCL ---|:---:|:---:|:---: Language | Rust | C++ | C++ License | MIT | GPLv3 | BSD-4-Clause-like Monolithic Files | Decode | Encode + Decode | Encode + Decode Distributed Files | ❌ | ❌ | ❌ N-D Images | ✅ | ❌ | ❌ Pixel Sample Formats | Scalar, Complex | Agnostic (Raw Bytes Only) | Scalar¹, Complex Image Metadata | Attributes, FITS Keywords |

Attributes², FITS Keywords³, XISF Properties, Thumbnail, CFA, ICC Profile

Attributes⁴, FITS Keywords, XISF Properties, Thumbnail, CFA, ICC Profile, RGB Working Space, Display Function, Resolution

Supported XISF Property Locations | ❌ | <Image>⁵ | <Image>, <Metadata>, <xisf> <Table> Element | ❌ | ❌ | ❌ <Reference> Element | ✅ | ❌ | ❌ Data Block Compression |

✅

zlib, lz4, lz4hc

✅⁶

zlib, lz4, lz4hc, zstd

✅

zlib, lz4, lz4hc

Checksum Verification | ✅ | ❌ | ✅ XML Digital Signature Verification | ❌ | ❌ | ❌

Does not support 64-bit integers
Only mandatory attributes and colorSpace
Raw strings only; cannot parse values
Missing imageType, offset, orientation, and uuid attributes
Int32, Float32, Float64, String, and TimePoint only
Sub-blocks not yet supported (this limits supported images to 4GiB); zstd support is nonstandard

Dependencies

Minimum Supported Rust Version (MSRV): 1.64.0, verified for x86_64-unknown-linux-gnu
libxml2
lz4
Can be configured to use zlib or zlib-ng

Road Map

[x] Read raw images
[x] Data block compression
[x] Checksum verification
[x] Images of complex numbers
[x] <Reference> element
[x] <FITSKeyword> element
[ ] Write monolithic files
[ ] Scalar, Complex, String, and TimePoint <Property> elements
[ ] Image thumbnails: turn read_data into a trait
[ ] Documentation and tests
[ ] CIE L*a*b color space conversion -- is this out of scope?
[ ] Remote resources
- Ask user to trust a specific source before connecting -- caching or permanently saving preferences per source address is out of scope
- remotefs crate? Covers (S)FTP+SCP+SMB+S3, that plus an HTTP(S) client should cover most use cases. the SMB library is GPLv3 though :(
- Some kind of file cache to avoid re-downloading? Consider tempfile crate. Check for changes in file size and last modified with stat to ensure up-to-date, and make an option to re-download a specific file in DataBlock's read functions
- HTTP(S) supports a more fine-grained cache with ETag/If-None-Match, Last-Modified/If-Modified-Since and Cache-Control headers
[ ] Vector, Matrix <Property> elements
- Need to look at cfitsio for inspiration here
[ ] XML Digital Signature verification
[ ] 128-bit floating point <Property> types (rustc_apfloat::ieee::Quad? fixed::F128?)
- Neither support any kind of math, but fixed::F128 supports bytemuck, which gives it an advantage
[ ] async data block read functions
- See async_compression crate
[ ] C/C++11 interface with cbindgen
[ ] zstd support? Nonstandard, but libXISF is doing it, and that seems to be the implementation that's catching on in the C++ world