rastra

An image toolkit for the browser. Native decoders first, wasm only where the platform cannot.

Status: 0.1, early. The API is frozen for 0.1 but not stable across 0.x.

Install

npm install rastra

Use

import { selectEncoder } from 'rastra';
import { probeCapabilities } from 'rastra/capability';

const report = await probeCapabilities();
const choice = selectEncoder('avif', report);

if (choice.available) {
  const bytes = await choice.encoder.encode({ data, width, height }, { quality: 70 });
}

choice.via is platform where the browser does the work and downloads nothing, or artifact where a wasm codec is fetched. choice.downloadBytes says what that costs before you commit to it. When it is not available you get what is missing rather than a failure later.

Serving the artifacts

Wasm codecs are separate files, served by your app with immutable caching:

import { setArtifactBase } from 'rastra';
setArtifactBase('/rastra/');

Copy node_modules/rastra/vendor/ to that path. Each artifact records its upstream source, version, licence and a hash per file in its artifact.json, and ARTIFACTS exposes the same records for generating a licence page.

Verifying it yourself

The capability report is built by decoding real fixtures and reading encoder output back, not by feature sniffing. Those fixtures are published, so you can re-run the same verification in your own browser:

import { FIXTURE_LOADERS, fixtureBytes } from 'rastra/fixtures';

Per-browser measurements from our own runs live in measurements/ in the repository, with the browser versions and dates they were taken.

Licence

MIT for the toolkit. Vendored codecs keep their own licences, recorded per artifact: Apache-2.0 for libavif, LGPL-3.0 for libheif. No GPL is shipped.