@undecaf/zbar-wasm

v0.11.0

Published

6 months ago

A WebAssembly build of the C/C++ ZBar barcode reader

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undecaf

zbar barcode qrcode scanner wasm webassembly emscripten

A WebAssembly build of the ZBar Bar Code Reader

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This project was forked from ZBar.wasm, a WebAssembly build of the ZBar Bar Code Reader written in C/C++.

Features

Provided as minified ES module, CommonJS module and plain script
Runs in modern browsers, in Node.js and also in workers
Deployment size approx. 330 kByte
Supports Code-39, Code-93, Code-128, Codabar, Databar/Expanded, EAN/GTIN-5/8/13, ISBN-10/13, ISBN-13+2, ISBN-13+5, ITF (Interleaved 2 of 5), QR Code, UPC-A/E.
Detects multiple barcodes per frame, also with different types
Barcodes may be oriented horizontally or vertically
Scans ImageData and RGB/grayscale ArrayBuffer objects
Outperforms pure JavaScript barcode scanners

:warning: zbar-wasm versions 0.10 and above contain breaking changes with respect to version 0.9, please refer to section Bundling/deploying zbar-wasm.

Examples based on zbar-wasm

A simple example: on GitHub (source code), on CodePen
A polyfill for the BarcodeDetector Web API: on GitHub (source code with build scripts for Rollup and esbuild), on CodePen

Getting started

Using zbar-wasm as `<script type="module">`

An example that scans a static image file:

<!DOCTYPE html>
<html>
<body>
  <img id="img" crossorigin="anonymous" src="https://raw.githubusercontent.com/undecaf/zbar-wasm/master/tests/img/qr_code.png">
  <pre id="result"></pre>

  <script type="module">
    import * as zbarWasm from 'https://cdn.jsdelivr.net/npm/@undecaf/[email protected]/dist/index.js'

    (async () => {
      const
        img = document.getElementById('img'),
        result = document.getElementById('result'),
        canvas = document.createElement('canvas'),
        context = canvas.getContext('2d');

      await img.decode()
      canvas.width = img.naturalWidth
      canvas.height = img.naturalHeight
      context.drawImage(img, 0, 0)

      const
        imageData = context.getImageData(0, 0, canvas.width, canvas.height),
        symbols = await zbarWasm.scanImageData(imageData);
      
      symbols.forEach(s => s.rawData = s.decode())
      result.innerText = JSON.stringify(symbols, null, 2)
    })()
  </script>
</body>
</html>

Using zbar-wasm as plain `<script>`

Almost identical to the snippet above, just replace the lines

    ⁝
  <script type="module">
    import * as zbarWasm from 'https://cdn.jsdelivr.net/npm/@undecaf/[email protected]/dist/index.js'
    ⁝

with

    ⁝
  <script src="https://cdn.jsdelivr.net/npm/@undecaf/[email protected]/dist/index.js"></script>
  <script>
    ⁝

Using zbar-wasm as an ESM or CommonJS module in Node.js

Installing:

$ npm install @undecaf/[email protected]
    or
$ yarn add @undecaf/[email protected]

Using:

import ... from '@undecaf/zbar-wasm' pulls the ES module from the package, require('@undecaf/zbar-wasm') pulls the CommonJS module.

Please refer to the API documentation for what can be imported/required.

A simple ES module that scans a static image file:

import { createCanvas, loadImage }  from 'canvas';
import { scanImageData } from '@undecaf/zbar-wasm';

(async (url) => {
  const
          img = await loadImage(url),
          canvas = createCanvas(img.width, img.height),
          ctx = canvas.getContext('2d');

  ctx.drawImage(img, 0, 0)

  const
          imageData = ctx.getImageData(0, 0, img.width, img.height),
          symbols = await scanImageData(imageData);

  console.log(symbols[0]?.typeName, symbols[0]?.decode())
})('https://raw.githubusercontent.com/undecaf/zbar-wasm/master/tests/img/qr_code.png')

For a CommonJS module, just replace the first lines with

const { createCanvas, loadImage } = require('canvas');
const { scanImageData } = require('@undecaf/zbar-wasm');

Bundling/deploying zbar-wasm

Barcode scanning is always delegated to the WebAssembly code in file zbar.wasm. zbar-wasm provides various functionally equivalent ESM and CommonJS modules for Node.js and for browsers that differ in how zbar.wasm is to be provided at runtime:

zbar.wasm can be loaded from a CDN by browsers.
zbar.wasm can be bundled as an asset. That asset should be served to browsers as application/wasm so that it can be compiled in parallel with being received.
Several zbar-wasm modules contain zbar.wasm as inline data.

The following overview shows the modules that are available in zbar-wasm. One of them needs to be bundled in your application.

| Path in package | Module type | Node core modules polyfilled(suitable for browsers) | zbar.wasm inlined | |:--------------------------|:-----------:|:-------------------------------------------------------:|:-------------------:| | /dist/index.mjs | ESM | :heavy_check_mark: | | | /dist/index.js | CommonJS | :heavy_check_mark: | | | /dist/main.mjs | ESM | | | | /dist/main.cjs | CommonJS | | | | /dist/inlined/index.mjs | ESM | :heavy_check_mark: | :heavy_check_mark: | | /dist/inlined/index.js | CommonJS | :heavy_check_mark: | :heavy_check_mark: | | /dist/inlined/main.mjs | ESM | | :heavy_check_mark: | | /dist/inlined/main.cjs | CommonJS | | :heavy_check_mark: |

The package entry points of zbar-wasm have been chosen so that bundlers will emit the appropriate module by default in most cases. However, zbar.wasm as inline data requires a suitable export condition in the bundler configuration, typically 'zbar-inlined'. Please refer to the exports section of package.json for details.

Building zbar-wasm includes testing the bundling process with Webpack, Rollup and esbuild and also testing the resulting bundles. The bundler configuration files tests/{webpack,rollup,esbuild}.config.js may be used as a reference of how to achieve a particular bundling result. Each of them covers the following combinations of platforms, module types and zbar.wasm provisioning for the respective bundler:

| zbar.wasm | Node module types | Browser module types | |:------------------|:-----------------:|:---------------------:| | loaded from CDN | | ESM, plain <script> | | bundled as asset | ESM, CommonJS | ESM | | inlined in module | ESM, CommonJS | ESM, plain <script> |

Loading `zbar.wasm` from a custom location

As a last resort, if you cannot make your bundler place zbar.wasm where it can be located by the script, you can specify an URL or path for that WASM file at runtime:

import { scanImageData, setModuleArgs } from '@undecaf/zbar-wasm';
    ⁝
// Call this function once at the beginning
setModuleArgs({
  /**
   * This function must return the URL or path of the WASM file.
   * 
   * @param filename default WASM filename ('zbar.wasm')
   * @param directory default WASM directory (URL or directory of the current script)
   * @returns {string} URL or path of the WASM file
   */
  locateFile: (filename, directory) => {
      return 'file:///your/wasm/directory/zbar.wasm'
  }   
});
    ⁝
// Then use the scanner
const symbols = await scanImageData(...);

API documentation

Owing to the predecessor of this project, samsam2310/zbar.wasm, a wiki and an extensive API Reference are already available. Many thanks to the author!

Please note that a few classes have been renamed compared to the documentation in order to avoid conflicts with built-in JavaScript class names:

Symbol → ZBarSymbol
Image → ZBarImage
ImageScanner → ZBarScanner

`BarcodeDetector` Web API

The BarcodeDetector polyfill package (in this repository, by the same author) is based on zbar-wasm but provides a standardized, higher-level and more flexible API.

Building zbar-wasm from source

Prerequisites:

A Linux platform
GNU make, tar and curl
Docker or Podman
Node.js v16+
At least one of the browsers supported by TestCafé

To build:

Clone this repository:

$ git clone https://github.com/undecaf/zbar-wasm
$ cd zbar-wasm

Enter your browser(s) in .testcaferc.json (supported browsers).
Enter two available port numbers in tests/src/ports.js.
If you prefer Podman as container engine then replace
```
EM_ENGINE = $(EM_DOCKER)
```
with
```
EM_ENGINE = $(EM_PODMAN)
```
in the provided Makefile.
Run the build process:
```
$ make
```
The make command runs emscripten in a container, compiling the C/C++ sources of the ZBar Bar Code Reader to WebAssembly. It also compiles and bundles the TypeScript glue code and runs the tests in Node.js and in the selected browser(s) on the host machine.

Credits to ...

samsam2310 for providing invaluable information in his zbar.wasm repository
mchehab for maintaining zbar
the emscripten folks for their compiler toolchain
the contributors to this package

License

Software: LGPL-2.1

Documentation: CC-BY-SA 4.0

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