A WebAssembly polyfill for the Barcode Detection API

!Minified size
!Open issues
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!License

This package polyfills the Barcode Detection API for browsers,
using a WebAssembly build of the
ZBar Bar Code Reader that is written in C/C++.
It offers the following features:

+ Polyfills the BarcodeDetector class
+ Supports these barcode formats: codabar, code_39, code_93, code_128, databar, databar_exp, ean_2, ean_5,
ean_8, ean_13, ean_13+2, ean_13+5, isbn_10, isbn_13, isbn_13+2, isbn_13+5, itf,
qr_code, sq_code, upc_a, upc_e
+ Not supported: aztec, data_matrix, pdf417
+ Scans , and live elements, image and video Blobs and Files and more
+ Can be used in Web Workers
+ Detects multiple barcodes per frame, also with different types
+ Barcodes may be oriented horizontally or vertically
+ Outperforms pure JavaScript polyfills

An online example is available on GitHub
(source code with build scripts for Rollup and esbuild)
and on CodePen.

Polyfilling BarcodeDetector

$3

Install:

``shell
$ npm install @undecaf/barcode-detector-polyfill
or
$ yarn add @undecaf/barcode-detector-polyfill
`

Make the polyfill available if necessary:

`javascript
import { BarcodeDetectorPolyfill } from '@undecaf/barcode-detector-polyfill'

try {
window['BarcodeDetector'].getSupportedFormats()
} catch {
window['BarcodeDetector'] = BarcodeDetectorPolyfill
}
⁝
`

Detailed examples are available here
(source code)
and here
(source code).

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Import the BarcodeDetectorPolyfill API:

`html

`

A detailed example is available here
(source code).

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Expose the BarcodeDetectorPolyfill API in variable barcodeDetectorPolyfill:

`html



`

A detailed example is available here
(source code).

Using BarcodeDetector/BarcodeDetectorPolyfill

$3

`javascript
const formats = await BarcodeDetector.getSupportedFormats()
`

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`javascript
const detector = new BarcodeDetector({ formats: ['code_39', 'code_128', 'ean_13'] })
`

If formats is omitted then all supported formats will be detected.


Where applicable (e.g. format 'qr_code'), text is assumed to be UTF-8 encoded. As an extension to the
BarcodeDetector API, a different encoding can be set for the BarcodeDetectorPolyfill:

`javascript
const detector = new BarcodeDetectorPolyfill({
formats: ['qr_code'],
zbar: {
encoding: 'iso-8859-15'
}
})
`

encoding may be any of the Encoding API encodings.

$3

`javascript
const barcodes = await detector.detect(source)
`

source must be an object of which an ImageBitmap
can be obtained, or else a
TypeError
will be thrown:

+ an element (HTMLImageElement),
must be completely loaded, or else a DOMException
will be thrown as InvalidStateError
+ a SVG element (SVGImageElement)
+ a element (HTMLCanvasElement)
+ a CanvasRenderingContext2D
+ an OffscreenCanvas ①
+ an OffscreenCanvasRenderingContext2D ①
+ a

① Also available in Web Workers

In addition, any object with a zero width or height property will be tolerated.

The detector processes the source in natural size, making detection results independent of the size rendered
by the browser.

Detected barcodes are stored as an array of objects in barcodes since source may contain multiple barcodes.
Each object has the following properties
(see here for details):

+ format: the detected barcode format (one of the formats specified as constructor options)
+ rawValue: the decoded barcode, always a string decoded from raw data as specified
+ boundingBox: the DOMRectReadOnly enclosing the
barcode in the source
+ cornerPoints: an arry of four {x, y} pairs in clockwise order, representing four corner points of the detected barcode.
BarcodeDetectorPolyfill returns the boundingBox corner points.

Additional properties provided only by BarcodeDetectorPolyfill:
+ orientation: 0 → image is upright, 1 → rotated 90° clockwise, 2 → upside down,
3 → rotated 90° counterclockwise, -1 → unknown
+ quality: a positive integer indicating the barcode quality as seen by the detector,
specific to each format

If an error occurs during barcode detection then the detect() method returns a rejected
Promise
containing the error.

Peculiarities owed to the underlying ZBar Bar Code Reader:
+ ISBN-10 will be scanned as ISBN-13 or EAN-13 if these are among the accepted formats
+ EAN-13+ will be scanned as ISBN-13+ if any ISBN-* is among the accepted formats

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Type definitions for BarcodeDetectorPolyfill, for constructor and method parameter types and for result types
are provided in @undecaf/barcode-detector-polyfill/dist/main.d.ts.

Build configurations

$3

This package
is under the MIT license although it depends on @undecaf/zbar-wasm
which is under LGPL.
Nevertheless, @undecaf/zbar-wasm may be bundled in your project as this does not violate the LGPL requirements.

Module @undecaf/zbar-wasm, however, expects the WASM file zbar.wasm to be located at the same path as itself;
details can be found in the documentation of @undecaf/zbar-wasm.
Therefore, bundlers must be configured accordingly. Configuration examples for Rollup and esbuild
can be found in directory example-bundled.
They were used to bundle the JavaScript code for this online example
in docs/example-bundled.

$3

~~In order to comply with the LGPL, @undecaf/zbar-wasm must not be bundled but may only be loaded as a library at runtime.~~
@undecaf/zbar-wasm can also be loaded at runtime, by default from https://cdn.jsdelivr.net. It can also be fetched from
a different endpoint if desired.

Bundlers must be configured so that they treat @undecaf/zbar-wasm as an external dependency instead of trying to resolve it.
Configuration examples for Rollup and esbuild
can be found in directory example-loaded.
They were used to bundle the JavaScript code for this online example
in docs/example-loaded.
They also illustrate how to load @undecaf/zbar-wasm from a non-default endpoint.

Credits to ...

+ lekoala for his barcode-detector-zbar`
that has an extensive list of useful links
+ the makers of Rollup and esbuild for their bundlers
which I consider a pleasure to work with

Disclaimer

I, the author of this document, have compiled it to the best of my knowledge, but it still expresses my personal opinion.
Therefore, in addition to what the licenses mentioned below state, I hereby decline any liability for
any false, inaccurate, inappropriate or incomplete information that may be presented here.

License

Software: MIT

Documentation: CC-BY-SA 4.0