mac4dstem.com

Source for mac4dstem.com, the website of the macEM suite: two free, native macOS applications for electron microscopy, mac4DSTEM (4D-STEM) and macTEM (TEM images, spectra and diffraction), and the six Swift kits they are built on.

The site is static: plain HTML, CSS, and vanilla JavaScript, with no build step, no dependencies, and no framework. Pushing to main publishes through GitHub Pages within about a minute.

Running it locally

Any static file server will do. From the repository root:

python3 -m http.server 4173

Then open http://localhost:4173. Pages reference assets by absolute path, so opening index.html directly from the filesystem will not load the stylesheet.

Structure

Path	Purpose
index.html	The mac4DSTEM page and landing page. Page-specific styling lives in its <style> block.
mactem/index.html	The macTEM page, in the landing page's style (its own <style> block, the demo left out).
privacy.html	Privacy policy for both applications and the site.
support.html	Support, requirements, and known limitations of both applications.
impressum.html	Provider identification (§ 5 DDG).
404.html	The page GitHub Pages serves for an unknown address.
assets/site.css	Styling shared across all pages.
assets/demo.js	The interactive virtual-imaging demo.
suite/	Kits overview, benchmarks and releases pages for the macEM suite. Generated, do not edit.
tools/build_suite_pages.py	Generates suite/ from the kits' and MacEMUI's CHANGELOG, docs/parity.md and docs/benchmarks.md. Run python3 tools/build_suite_pages.py --fetch after a kit or MacEMUI release.
tools/check_site.py	The CI check: internal links, and versions and download sizes against the GitHub releases.
tools/export_atlas.py	Regenerates the demo dataset. Development only.

Checks and releases

CI (.github/workflows/ci.yml) runs on every push to main, on pull requests, and once a day. It scans for references to private material and runs tools/check_site.py: every internal link and #fragment must resolve, each app page must state the latest release's version and .dmg size (in the text and in the JSON-LD), and suite/releases.html must name each kit's and MacEMUI's latest tag. Run it locally with python3 tools/check_site.py (or --offline for links only).

After an app release, update the version and size on its page. After a kit or MacEMUI release, regenerate suite/.

Everything else in assets/ is a generated artefact — images, icons, the social card, and the demo data. None of it is edited by hand.

The interactive demo

The landing page includes a working 4D-STEM virtual-imaging demo running entirely in the browser, on a real experimental scan of a NiCu alloy.

A 4D-STEM dataset records a full diffraction pattern at every probe position, so real space and diffraction space each produce the other. Placing a mask on the detector integrates it into a virtual image; selecting a region of the scan integrates it into a diffraction pattern. Both directions recompute in a few milliseconds, so the masks respond as you drag them.

How the data is shipped

The full datacube is far too large to serve, so tools/export_atlas.py reduces it to a single sprite atlas:

• The scan is binned 2×2 to 100×100 positions, keeping the atlas at 3200×3200 — below Safari's canvas area limit.
• Each 32×32 diffraction pattern becomes one tile, at pixel (rx*32, ry*32).
• Intensities are log-companded to 8 bits. Eight bits cannot hold the linear range between the direct beam and the dark-field signal, so the page rebuilds a 256-entry lookup table from demo-manifest.json and decompands before summing. Integrals therefore stay linear in the units the microscope recorded.

The atlas is stored losslessly. Lossy compression was measured introducing up to 9% error in dark-field sums even at high quality, because adjacent tiles are unrelated patterns and the codec bleeds signal across tile boundaries.

The atlas is only fetched when the demo is approached, and never on metered or slow connections, where a load button appears instead.

Regenerating it

Place the source .h5 datacube in datacube/ (gitignored — it is far above GitHub's file size limit) and run:

pip install h5py numpy pillow

python3 tools/export_atlas.py [--src FILE.h5] [--previews DIR]

This rewrites assets/demo-atlas.png and assets/demo-manifest.json; --previews also writes mean-pattern, bright-field and dark-field check images to DIR.

Privacy

The site sets no cookies, runs no analytics, and makes no third-party requests. It uses the system font stack rather than a hosted webfont. See privacy.html.

Licence

The site is released under the GNU General Public License v3.0 (LICENSE), as are both applications and the kits. mac4DSTEM's analysis algorithms are ported from and validated against py4DSTEM; work published using mac4DSTEM should cite py4DSTEM for the underlying methods.

Contact

mail@mac4dstem.com