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JavaScript Hello World Sample - Read An Image

In most cases, users of Dynamsoft Barcode Reader JavaScript SDK (hereafter called “the library”) reads barcodes from a video input. In this article, we will discuss an uncommon usage of the library: reading barcodes from existing images.

Official Sample

Preparation

In this article, we’ll make use of the library through the jsDelivr CDN. Make sure you can access this file “https://cdn.jsdelivr.net/npm/dynamsoft-javascript-barcode@8.4.0/dist/dbr.js”.

Create the sample page

Create an empty web page and name it “read-an-image.html” with the following code:

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0">
    <title>Dynamsoft Barcode Reader Sample - Read an Image</title>
</head>

<body>
    <script></script>
</body>

</html>

Add reference to the library in the page “head”.

<script src="https://cdn.jsdelivr.net/npm/dynamsoft-javascript-barcode@8.4.0/dist/dbr.js"></script>

In the page “body”, add an input for image selecting and a div for displaying the barcode results.

<input id="ipt-file" type="file" accept="image/png,image/jpeg,image/bmp,image/gif">
<div id="results"></div>

Add an event listner for the file input, then add barcode reading code in the callback.

let pReader = null;
document.getElementById('ipt-file').addEventListener('change', async function() {
    try {
        let resDIV = document.getElementById('results');
        let reader = await (pReader = pReader || Dynamsoft.DBR.BarcodeReader.createInstance());
        for (let i = 0; i < this.files.length; ++i) {
            // Actually there will only be one file here (no 'multiple' attribute)
            let file = this.files[i];
            // Decode the file
            let results = await reader.decode(file);
            if (results.length === 0) {
                resDIV.innerHTML = "No Barcode Found!";
                return;
            }
            var info = "";
            for (let result of results) {
                info += "<p>" + result.barcodeFormatString + ": " + result.barcodeText + "</p>";
            }
            resDIV.innerHTML = info;
        }
    } catch (ex) {
        alert(ex.message);
    }
});

NOTE

An instance of the library is created when an image is selected for the first time.

The method decode() takes the file as the input, reads it and returns the results.

In your application, the input may not be a file, the method decode() can handle the following types of input: Blob, Buffer, ArrayBuffer, Uint8Array, Uint8ClampedArray, HTMLImageElement, HTMLCanvasElement, HTMLVideoElement, string.