WebcamBarcodeScanner

This is an library that allows you to use your webcam as a barcode scanner.

This library is part of @point-of-sale, a collection of libraries for interfacing browsers and Node with Point of Sale devices such as receipt printers, barcode scanners and customer facing displays.

What does this library do?

This library uses the same API as WebSerialBarcodeScanner and WebHIDBarcodeScanner, which allows you to use external barcode scanners. But if you do not have an external barcode scanner, you can use this library as a drop-in replacement, or a fallback option using the webcam of your laptop or phone.

How to use it?

Load the webcam-barcode-scanner.umd.js file from the dist directory in the browser and instantiate a WebcamBarcodeScanner object.

<script src='webcam-barcode-scanner.umd.js'></script>

<script>

    const barcodeScanner = new WebcamBarcodeScanner();

</script>

Or import the webcam-barcode-scanner.esm.js module:

import WebcamBarcodeScanner from 'webcam-barcode-scanner.esm.js';

const barcodeScanner = new WebcamBarcodeScanner();

Configuration

When you create the WebcamBarcodeScanner object you can specify a number of options to help with the library with connecting to the device.

Symbologies

By default this library will return barcodes of every symbology. However if you want to use this library in a specific environment, such as retail, you can limit this library to only allow symbologies that are used in retail, for example:

const barcodeScanner = new WebcamBarcodeScanner({
    allowedSymbologies: [ 'ean13', 'ean8', 'upca', 'upce', 'qr-code' ]
});

This will allow all EAN and UPC barcodes. But also QR-codes because the retail industry is moving to the QR code based GS Digital Links in the coming years. These digital links contain an URL and can be used by consumers to read more about the product they are buying or have bought. But it also includes the Global Trade Identification Number (GTIN) that is also used by EAN and UPC barcodes.

If we find GS1 data such as the GTIN in the scanned barcode we will automatically decode it and place it in the data property:

barcodeScanner.addEventListener('barcode', e => {
    if (e.data?.gtin) {
        console.log(`Found barcode with GTIN ${e.data.gtin}`);
    }
});

Fallback worker support

By default this library will try to use the build-in barcode detector support in Chromium browsers. As a fallback it uses a WASM version of ZXing running in a worker. It will try to load the worker from the same directory as the UMD or ESM module. But if you use a bundler that will fail and the barcode detection will run in the main thread. That is something you want to prevent by providing the library with the correct path to the worker library:

const barcodeScanner = new WebcamBarcodeScanner({
    workerPath: '/dist/webcam-barcode-scanner.worker.js'
});

Similarly you configure the path to the binary WASM file as well:

const barcodeScanner = new WebcamBarcodeScanner({
    workerPath: '/dist/webcam-barcode-scanner.worker.js',
    binaryPath: '/dist/webcam-barcode-scanner.wasm'
});

If you want to force the library to use WASM - which we would not advice - you can force the fallback:

const barcodeScanner = new WebcamBarcodeScanner({
    useFallback: true
});

If you want to force the library to use the main thread instead of a worker - again, which we would not advice - you can force this:

const barcodeScanner = new WebcamBarcodeScanner({
    useWorker: false
});

Beep on scan

By default this library will beep on a succesful scan, to mimick the sound an actual barcode scanner would make. If you want to disable this, you can do so:

const barcodeScanner = new WebcamBarcodeScanner({
    beepOnScan: false
});

Preview window

This library will show a small preview overlay on top of the current webpage with a view of your webcam. This will allow you to easily position the barcode in the right spot.

You can configure the preview with the following options:

• enabled Turn the preview on or off
• draggable Allow the preview to be dragged to a different corner, disabled by default
• mirrored Mirror the image in the preview, so that movement mirrors your own
• hud Paint a border around detected barcodes on the preview
• size Size of the preview in pixels
• position Position of the preview, for example: top-left, bottom-left, top-right and bottom-right.
• padding Space between the preview and the corner of the window, either a number, or an object with the properties: top, right, bottom and left
• radius Border radius of the preview
• zIndex Specify a z-index to make sure it is on top of your own content

For example:

const barcodeScanner = new WebcamBarcodeScanner({
    preview: {
        enabled: false
    }
});

Or:

const barcodeScanner = new WebcamBarcodeScanner({
    preview: {
        draggable: true
    }
});

Or:

const barcodeScanner = new WebcamBarcodeScanner({
    preview: {
        size: 		320,
        position: 	'bottom-left',
        padding: 	{
            top:        100,
            left:       20,
            right:      20,
            bottom:     20
        },
        radius: 	10
    }
});

Connect to a scanner

The first time you have to manually connect to the barcode scanner by calling the connect() function. This function must be called as the result of an user action, for example clicking a button. You cannot call this function on page load.

function handleConnectButtonClick() {
    barcodeScanner.connect();
}

Subsequent times you can simply call the reconnect() function. You have to provide an object with vendor id and product id of the previously connected barcode scanner in order to find the correct barcode scanner and connect to it again. If there is more than one device with the same vendor id and product id it won't be able to determine which of the two devices was previously used. So it will not reconnect. You can get the vendor id and product id by listening to the connected event and store it for later use. Unfortunately this is only available for USB connected devices. It is recommended to call this button on page load to prevent having to manually connect to a previously connected device.

    barcodeScanner.reconnect(lastUsedDevice);

If there are no barcode scanners connected that have been previously connected, this function will do nothing.

However, this library will actively look for new devices being connected. So if you connect a previously connected barcode scanner, it will immediately become available.

To find out when a barcode scanner is connected you can listen for the connected event using the addEventListener() function.

barcodeScanner.addEventListener('connected', device => {
    console.log(`Connected to a webcam ${device.deviceId}`);

    /* Store device for reconnecting */
    lastUsedDevice = device;
});

The callback of the connected event is passed an object with the following properties:

• type Type of the connection that is used, in this case it is always webcam.
• deviceId The device id of the webcam.

To find out when the webcam is disconnected you can listen for the disconnected event using the addEventListener() function.

barcodeScanner.addEventListener('disconnected', () => {
    console.log(`Disconnected`);
});

You can force the webcam to disconnect by calling the disconnect() function:

barcodeScanner.disconnect();

Events

Once connected you can use listen for the following events to receive data from the barcode scanner.

Scanning barcodes

Whenever the libary detects a barcode, it will send out a barcode event that you can listen for.

barcodeScanner.addEventListener('barcode', e => {
    console.log(`Found barcode ${e.value}`);
});

The callback is passed an object with the following properties:

• value The value of the barcode as a string
• data If the barcode contains GS1 data, such as the Global Trade Identification Number (GTIN) the data will be parsed into elements.
• aim Optionally, the AIM Code ID, which is a 3 character ISO/IEC identifier and gives information about the symbology of the barcode which was scanned. The AIM Code ID will typically only be available when fallback mode is used, as the build-in barcode scanner functionality does not provide this data.
• symbology Optionally a library specific identifier of the symbology.
• bytes The raw bytes we've received from the scanner. This propery is an array containing one or more Uint8Array's.

Parsed GS1 data

The data property is optional, but if GS1 data is detected, it will contain an object with the following properties:

• gtin Optionally, if the GS1 elements define a GTIN, it will be listed here for quick reference.
• elements An array of all the GS1 elements that the barcode contains. Each element is an object with the folowing properties; ai: the appication identifier, label: a human readable label and value: the value of the element.

Symbologies

The symbology property can be any of the following common values for 1D barcodes:

ean8, ean13, upca, upce, code39, code93, code128, codabar, interleaved-2-of-5, gs1-databar-omni, gs1-databar-expanded

Or these 2D barcodes:

qr-code, qr-code-micro, data-matrix, maxicode, aztec-code, pdf417

Example

A typical EAN 13 barcode would look like:

{
    value: "3046920029759",
    symbology: "ean13",
    aim: "]E0",
    data: {
        gtin: "03046920029759",
        elements: [{
            ai: "01",
            label: "GTIN",
            value: "03046920029759"
        }]
    },
    bytes: [[
        0x30, 0x33, 0x30, 0x34, 0x36, 0x39, 0x32, 0x30, 
        0x30, 0x32, 0x1D, 0x37, 0x35, 0x39
    ]]
}

This library has been created by Niels Leenheer under the MIT license. Feel free to use it in your products. The development of this library is sponsored by Salonhub.