@fits-js/core

FITS parser, image decoder, and byte-source readers for JavaScript runtimes, in pure TypeScript with zero runtime dependencies.

Note: This project is in early development and is not recommended for production usage, but feedback is very welcome on GitHub.

Install

npm install @fits-js/core

Requires Node 22 or later. In the browser, any environment with fetch, Blob, and TypedArray works.

Quick example

import { NodeFileReader, openFits, readImage } from "@fits-js/core";

const reader = await NodeFileReader.open("data/image.fits");
try {
  const { hdus } = await openFits(reader);
  const region = { start: [0, 0], shape: [16, 16] };
  const { data } = await readImage(hdus[0], reader, { region });
  console.log(data.slice(0, 8));
} finally {
  await reader.close();
}

Public surface

• openFits(reader) enumerates HDUs lazily, reading only header blocks.
• readImage(hdu, reader, { region? }) decodes a 2D or higher image HDU. With a region, only the bytes covering that cutout are fetched.
• RandomAccessReader implementations: BytesReader (in-memory), BlobReader (browser Blob/File), HttpRangeReader (HTTP Range with LRU paging and If-Range), NodeFileReader (fs-backed).
• FitsHeader with typed accessors (getNumber, getString, getBoolean, get, getAll).
• Typed error hierarchy: FitsError, FitsHeaderError, FitsStructureError, FitsUnsupportedError, FitsIoError.

Documentation

Full docs at prustic.github.io/fits-js.

• Quickstart
• Reading a FITS file
• Reading over HTTP
• Working with image data
• Error handling
• Roadmap

License

Apache-2.0