xisf-rs

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/Apache	GPLv3	BSD-4-Clause-like
Monolithic Files	Read	Read + Write	Read + Write
Distributed Files	Read (Partial) http, https, ftp, see road map	❌	❌
N-D Images	✅	❌	❌
Pixel Sample Formats	Scalar, Complex	Agnostic (Raw Bytes Only)	Scalar1, Complex
Image Metadata	Everything Attributes, XISF Properties, FITS Keywords, ICC Profile, RGB Working Space, Display Function, CFA, Resolution, Thumbnail	Basic Attributes2, XISF Properties3, FITS Keywords4, ICC Profile, CFA, Thumbnail	Nearly Everything Attributes5, XISF Properties6, FITS Keywords, ICC Profile, RGB Working Space, Display Function, CFA, Resolution, Thumbnail
Supported XISF Property Locations	<Image>, <Metadata>, <xisf>	<Image>	<Image>, <Metadata>, <xisf>
<Table> Element	✅	❌	❌
<Reference> Element	✅	❌	❌
Data Block Compression	✅7   zlib, lz4, lz4hc, zstd	✅7, 8 zlib, lz4, lz4hc, zstd	✅7   zlib, lz4, lz4hc, zstd
Checksum Verification	✅	❌	✅
XML Digital Signature Verification	❌	❌	❌

Footnotes

1. Does not support 64-bit integer pixel samples
2. Only mandatory attributes and colorSpace
3. Int32, Float32, Float64, String, and TimePoint only
4. Raw strings only; cannot parse values
5. Missing imageType, offset, orientation, and uuid attributes
6. No 128-bit integer or floating point values
7. zstd support is nonstandard for spec version 1.0, but has been confirmed for an upcoming version of the standard
8. Sub-blocks not yet supported (this limits supported images to 4GiB)

Dependencies

• Minimum Supported Rust Version (MSRV): 1.67.0, verified for x86_64-unknown-linux-gnu
• libxml2 (MIT)
• lz4 (BSD-2-Clause)
• zstd (BSD-3-Clause)
• Can be configured to use zlib (Zlib) or zlib-ng (Zlib)
• gcc quadmath (LGPL v2.1) when the f128 feature is enabled
  • quadmath doesn't support every CPU architecture, so 128-bit floating point properties are limited to those architectures
• Test suite requires a Docker installation when the remote-ftp feature is enabled

Road Map

• Read N-dimensional images
• Data block compression
• Checksum verification
• Images of complex numbers
• <Reference> element
• <FITSKeyword> element
• Image thumbnails
• Remote resources
  • Ask user for trust before connecting
  • Caching
    • Files with a checksum are read through twice, and right now that means the file gets downloaded twice
  • Authorization/Credentials Store
    • Stateful schemes like FTP require keeping track of sessions
  • XISB files
  • SFTP/SCP
• Non-<Property> image metadata
• Scalar, Complex, String, and TimePoint <Property> elements
• Vector, Matrix <Property> elements
• 128-bit floating point <Property> types
• Write monolithic files
• <Table> element
• Property format strings
• Write distributed files
• Color space conversion?
• XML Digital Signature verification
• async data block read functions
• C/C++11 interface with cbindgen