HEALPix

Introduction

This module is an implementation of HEALPix in TypeScript. A Javascript version is available as well. (Typescript is a typed superset of Javascript, that compiles to Javascript.)

This package was implemented based on the description in the HEALPix paper. Pixelisation-related functions (including corners) and disk query are available for the ring and nested HEALPix pixelisation schemes. Most API interfaces are ported from wonderful healpy Python package, and tests against healpy are used to show correctness.

The following sections explain installation and usage, and give examples. Detailed API documentation is also available.

Limitations

• This package can handle only norder <= 15.

Installation and Usage

With NPM

If you are using Node.js, you can download and install @hscmap/healpix with npm:

npm install --save @hscmap/healpix

Then from your Javascript (JS) you can require and use healpix like this:

const healpix = require('@hscmap/healpix');
console.log(healpix.order2nside(0));

From Typescript import and use it like this:

import * as healpix from '@hscmap/healpix';
console.log(healpix.order2nside(0));

Standalone JS

Another option is to use healpix.js as a standalone library.

Thanks to the unpkg CDN, you can simply add this line to your HTML file:

<script src="https://unpkg.com/@hscmap/healpix@latest/standalone/dist/healpix.js"></script>

and after that line you can call healpix functions like this:

<script>
console.log(healpix.order2nside(0));
</script>

If you don't want to use the latest version, select one from here.

Examples

Examples using healpix are available here: http://michitaro.github.io/healpix/

The code is available here:

• docs/example/src/pixcoord2vec
• docs/example/src/query_disc

Instructions how to build the examples locally are in the next section.

Developer documentation

To hack on this package, clone https://github.com/michitaro/healpix from Github:

git clone https://github.com/michitaro/healpix.git
cd healpix

Then run npm install to install the tools and dependencies used (especially Typescript and Webpack):

npm install

The package is implemented in a single Typescript file: src/index.ts.

To generate the standalone Javascript package standalone/dist/healpix.js, run this command:

npm run standalone

To compile and run the examples locally:

npm run build-example

To test the package install Python and healpy first, and then run:

npm run my-test

Feedback, issues and contributions welcome: https://github.com/michitaro/healpix

See Also

• http://healpix.sourceforge.net
• https://healpy.readthedocs.io

License

This software is released under the MIT License, see LICENSE.