rustafits

High-performance FITS/XISF to JPEG/PNG converter for astronomical images with auto-stretch, Bayer debayering, and SIMD acceleration. Pure Rust — no system dependencies.

Features

• FITS & XISF Support: Native readers for both formats (no external libraries)
• Auto-Stretch: Median-based statistical stretching (PixInsight STF compatible)
• Bayer Debayering: Super-pixel 2x2 block averaging (RGGB, BGGR, GBRG, GRBG)
• Preview Mode: 2x2 binning for fast previews
• SIMD Optimized: SSE2/AVX2 (x86_64) and NEON (aarch64) with automatic detection
• In-Memory API: Get raw pixel data without file I/O — ideal for GUI apps

Supported Formats

Installation

Cargo (Recommended)

No system dependencies needed — everything is pure Rust:

cargo install rustafits

From Source

git clone https://github.com/eg013ra1n/rustafits
cd rustafits
cargo build --release
sudo cp target/release/rustafits /usr/local/bin/

Homebrew (macOS/Linux)

brew tap eg013ra1n/rustafits
brew install rustafits

CLI Usage

# Basic conversion
rustafits image.fits output.jpg
rustafits image.xisf output.png

# Fast preview (2x2 binning)
rustafits large.fits preview.jpg --preview

# Downscaled output
rustafits large.fits preview.jpg --downscale 4

# Options
rustafits <input> <output> [OPTIONS]
  --downscale <N>   Downscale factor (default: 1)
  --quality <Q>     JPEG quality 1-100 (default: 95)
  --no-debayer      Disable Bayer debayering
  --preview         2x2 binning for mono images
  --log             Show detailed information

Library Usage

Add to your Cargo.toml:

[dependencies]
rustafits = "0.4"

File output

use astroimage::ImageConverter;

ImageConverter::new()
    .with_preview_mode()
    .with_quality(90)
    .convert("input.fits", "output.jpg")?;

In-memory processing

Get raw RGB pixel data without writing to disk — useful for GUI viewers, web backends, and Tauri apps:

use astroimage::{ImageConverter, ProcessedImage};

let image: ProcessedImage = ImageConverter::new()
    .with_downscale(2)
    .process("input.fits")?;

// image.data     - Vec<u8>, interleaved RGB bytes
// image.width    - pixel width
// image.height   - pixel height
// image.is_color - true if debayered/RGB, false if mono (gray replicated to RGB)

Builder methods

Multi-image concurrent processing

By default, all parallel work (debayering, stretch, binning, byte conversion) runs on rayon's global thread pool. This works well for single-image processing, but when processing multiple images concurrently from separate threads, they all compete for the same pool — causing thread oversubscription and degraded throughput.

Use with_thread_pool() to route all parallel work to a dedicated or shared pool:

use std::sync::Arc;
use astroimage::{ImageConverter, ThreadPoolBuilder};

// Create a shared pool once at startup
let pool = Arc::new(
    ThreadPoolBuilder::new()
        .num_threads(num_cpus::get())
        .build()
        .unwrap()
);

// Process multiple images concurrently
let handles: Vec<_> = paths.iter().map(|path| {
    let pool = Arc::clone(&pool);
    let path = path.clone();
    std::thread::spawn(move || {
        ImageConverter::new()
            .with_thread_pool(pool)
            .process(&path)
    })
}).collect();

let results: Vec<_> = handles.into_iter()
    .map(|h| h.join().unwrap())
    .collect();

Recommendations by concurrency level:

Memory budget: Each full-resolution image (e.g. 4096x3072 16-bit) uses ~150 MB peak. For 10 concurrent images, budget ~1.5 GB. Use with_preview_mode() or with_downscale() to reduce memory usage.

Performance

Benchmarks on Apple M4 (6252x4176 16-bit images):

SIMD Acceleration

SIMD is used across the processing pipeline with automatic runtime dispatch:

Architecture

rustafits/
├── src/
│   ├── lib.rs              # Library entry + public API
│   ├── types.rs            # Core types (PixelData, ProcessedImage, etc.)
│   ├── converter.rs        # ImageConverter builder
│   ├── pipeline.rs         # Processing pipeline
│   ├── output.rs           # JPEG/PNG file output
│   ├── bin/rustafits.rs    # CLI tool
│   ├── formats/
│   │   ├── mod.rs          # Format dispatch
│   │   ├── fits.rs         # FITS reader
│   │   └── xisf.rs         # XISF reader (zlib/LZ4/Zstd)
│   └── processing/
│       ├── mod.rs           # Processing module
│       ├── stretch.rs       # Auto-stretch (SIMD)
│       ├── debayer.rs       # Bayer debayering (SIMD)
│       ├── binning.rs       # 2x2 binning (SIMD)
│       ├── downscale.rs     # Integer downscaling
│       └── color.rs         # Color conversions (SIMD)

Dependencies (all pure Rust): anyhow, flate2 (rust_backend), lz4_flex, ruzstd, image, quick-xml, base64

Troubleshooting

Slow conversion: Use --preview for mono images or --downscale 2

Black/white output: Run with --log to check stretch parameters

References

• PixInsight — Screen Transfer Function documentation
• FITS Standard
• XISF Specification

License

Apache-2.0