lean-qr/README.md

minimal QR code generation

# <img src="https://qr.davidje13.com/resources/logo.svg" alt="Lean QR" />

Lean QR is a lightweight yet fully-featured library for generating QR Codes.
It runs in NodeJS and all recent browsers, and includes wrapper components
for React and Preact. Under 4kB compressed.

## Features

- ISO 18004 compliant;
- Lightweight (less than 4kB compressed, ~7kB uncompressed, no dependencies);
- Simple yet flexible API, with sensible defaults for all configuration;
- Supports all [standard encodings](https://qr.davidje13.com/docs/#mode) out-of-the box:
  - including Unicode 😎;
  - and Shift-JIS 漢字;
  - and supports [custom modes](https://qr.davidje13.com/docs/#custom-modes) for special requirements;
- Automatic encoding to minimise output size;
- [Fast enough for lag-free live editing](https://qr.davidje13.com/docs/#comparison);
- Comprehensive automated testing;
- Multiple output formats ([canvas](https://qr.davidje13.com/docs/#Bitmap2D_toCanvas) / [PNG](https://qr.davidje13.com/docs/#toPngBuffer) / [SVG](https://qr.davidje13.com/docs/#toSvgSource) / [text](https://qr.davidje13.com/docs/#Bitmap2D_toString)).

You can [see it in action online](https://qr.davidje13.com/), or try it from the terminal:

```shell
npx lean-qr 'MY MESSAGE HERE'
```

## Basic Usage

See the [Quickstart](https://qr.davidje13.com/docs/#quickstart) documentation for NodeJS /
Browser / React / Preact / CLI usage.

```shell
npm install --save lean-qr
```

```html
<canvas id="my-qr-code" />

<style>
#my-qr-code {
  image-rendering: pixelated;
  width: 100%;
}
</style>
```

```javascript
import { generate } from 'lean-qr';

const qrCode = generate('LEAN-QR LIBRARY');
qrCode.toCanvas(document.getElementById('my-qr-code'));
```

## Troubleshooting

### Jest / JSDOM error: "TextEncoder is not defined"

There is a [bug in JSDOM](https://github.com/jsdom/jsdom/issues/2524) which
prevents this class being available in tests. This issue only affects JSDOM,
and can be fixed with:

```js
import { TextEncoder, TextDecoder } from 'node:util';
global.TextEncoder = TextEncoder;
global.TextDecoder = TextDecoder;
```

You can put this in the test file or in Jest's `setupFilesAfterEnv` config.
You should _not_ put this in your application code.

## Full Documentation

- [Quickstart](https://qr.davidje13.com/docs/#quickstart)
- [API Reference](https://qr.davidje13.com/docs/#api)
- [Migrating from Version 1.x to 2.x](https://qr.davidje13.com/docs/#v2)
- [Source Code](https://github.com/davidje13/lean-qr)
- [Comparison With Other Libraries](https://qr.davidje13.com/docs/#comparison)