Table of contents

Document Normalizer for Your Website - User Guide

Dynamsoft Document Normalizer JavaScript Edition (DDN-JS) is equipped with industry-leading quadrilateral detection and image normalization algorithms. Using its well-designed API, you can turn your web page into a document normalizer with a few lines of code.

version downloads jsdelivr vulnerabilities

Once the DDN-JS SDK is integrated into your web pages, your users can access a connected camera through their browser, point it at the document and detect the document’s boundaries in real-time. Once a detection looks promising, users can enter edit mode to fine-tune the boundaries before using them to obtain a normalized image of the document. The normalization process now includes cropping, perspective correction, brightness adjustment, contrast adjustment, and color mode conversion.

In this guide, you will learn how to integrate this SDK into your website step by step.

Table of Contents

Example Usage

Let’s start by testing an example of the SDK which demonstrates how to detect quadrilaterals (document boundaries) from a live video stream and use a selected quadrilateral to obtain a normalized image of the document. To run the example, the following are required

  1. Internet connection
  2. A supported browser
  3. An accessible Camera

Check the code

The complete code of the example is shown below:

<!DOCTYPE html>
<html lang="en">
<head>
    <script src="https://cdn.jsdelivr.net/npm/dynamsoft-camera-enhancer@3.1.0/dist/dce.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/dynamsoft-document-normalizer@1.0.11/dist/ddn.js"></script>
</head>
<body>
    <h1>Capture A Document</h1>
    <button id="confirmQuadForNormalization">Edit Boundaries</button>
    <button id="normalizeWithConfirmedQuad">Normalize and Capture</button>
    <div id="div-ui-container" style="margin-top: 10px;height: 70vh;"></div>
    <div id="normalized-result"></div>
    <script>
        let normalizer = null;
        let cameraEnhancer = null;

        // You can visit https://www.dynamsoft.com/customer/license/trialLicense?utm_source=npm&product=ddn&package=js to get your own trial license good for 30 days.
        Dynamsoft.DDN.DocumentNormalizer.license = "DLS2eyJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSJ9";

        (async function() {
            cameraEnhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
            normalizer = await Dynamsoft.DDN.DocumentNormalizer.createInstance();
            await normalizer.setImageSource(cameraEnhancer, { resultsHighlightBaseShapes: Dynamsoft.DCE.DrawingItem });

            await document.getElementById('div-ui-container').append(cameraEnhancer.getUIElement());
            
            // Triggered when a quadrilateral is detected from a video frame.
            normalizer.onQuadDetected = (quadResults, sourceImage) => {
              console.log(quadResults);
            };

            // Click the button to pause the video and edit a quadrilateral.
            document.getElementById('confirmQuadForNormalization').addEventListener("click", () => {
              normalizer.confirmQuadForNormalization();
            });

            // Click the button to normalize with the selected/adjusted quadrilateral.
            document.getElementById('normalizeWithConfirmedQuad').addEventListener("click", async () => {
              const normalizedImageResult = await normalizer.normalizeWithConfirmedQuad();
              if(normalizedImageResult) {
                // Show the normalized image in a Canvas
                const cvs = normalizedImageResult.image.toCanvas();
                document.querySelector("#normalized-result").appendChild(cvs);
                console.log(normalizedImageResult);
              }
            });
            // Start scanning document boundaries.
            await normalizer.startScanning(true);
          })();
    </script>
</body>

</html>

Run via JSFiddle

About the code

  • DocumentNormalizer.createInstance(): this method creates a DocumentNormalizer object called normalizer.

  • CameraEnhancer.createInstance(): this method creates a CameraEnhancer object called cameraEnhancer, which is used to control the camera as well as the default user interface. Once CameraEnhancer is bound to normalizer via setImageSource(), the normalizer will get video frames from the camera for detection and normalization.

  • onQuadDetected: this event is triggered every time the SDK finds at least one quadrilateral after scanning a video frame. The quadResults object contains all the found quadrilaterals. In this example, the results are logged in the browser console.

  • startScanning(true): starts continuous video frame scanning. It returns a Promise which resovles when the camera is opened, the video shows up on the page and begins to scan (which means the normalizer starts to get frames for detection).

  • confirmQuadForNormalization(): pauses the video stream and enter “editor mode” where the quadrilaterals in current frame are selectable and editable. You can select one quadrilateral that surrounds the target document and edit it to be as accurate as possible.

  • normalizeWithConfirmedQuad(): normalizes the image with the quadrilateral to obtain an image of the document as “normalizedImageResult”.

Test the code

Create a text file with the name “Normalize-Video-Frames.html”, fill it with the code above and save. After that, open the example page in a browser, allow the page to access your camera and the video will show up on the page. After that, you can point the camera at something with a quadrilateral border to detect it.

You can also just test it at https://jsfiddle.net/DynamsoftTeam/5vgh7rdx/

Please note:

  • Although the page should work properly when opened directly as a file (“file:///”), it’s recommended that you deploy it to a web server and access it via HTTPS.
  • On first use, you need to wait a few seconds for the SDK to initialize.
  • The license “DLS2eyJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSJ9” used in this sample is an online license and requires network connection to work.

If the test doesn’t go as expected, you can contact us.

Building your own page

In this section, we’ll break down and show all the steps required to build a web page for document capturing with DDN-JS.

Include the SDK

Use a CDN

The simplest way to include the SDK is to use either the jsDelivr or UNPKG CDN. The “hello world” example above uses jsDelivr. We should also include the SDK Dynamsoft Camera Enhancer which provides camera support.

  • jsDeliv

    <script src="https://cdn.jsdelivr.net/npm/dynamsoft-document-normalizer@1.0.11/dist/ddn.js"></script>
<script src="https://cdn.jsdelivr.net/npm/dynamsoft-camera-enhancer@3.1.0/dist/dce.js"></script>

  • UNPKG

    <script src="https://unpkg.com/dynamsoft-document-normalizer@1.0.11/dist/ddn.js"></script>
<script src="https://unpkg.com/dynamsoft-camera-enhancer@3.1.0/dist/dce.js"></script>

Host the SDK yourself

Besides using the CDN, you can also download the SDK and host its files on your own website / server before including it in your application.

Also read how to do the same for Dynamsoft Camera Enhancer.

To download the SDK:

  • yarn

    yarn add dynamsoft-document-normalizer@1.0.11

  • npm

    npm install dynamsoft-document-normalizer@1.0.11

Depending on how you downloaded the SDK and where you put it, you can typically include it like this:

  <script src="/dynamsoft-document-normalizer-js-1.0.11/dist/ddn.js"></script>

or

  <script src="/node_modules/dynamsoft-document-normalizer/dist/ddn.js"></script>

or

  import { DocumentNormalizer } from 'dynamsoft-document-normalizer';

Configure the SDK

Before using the SDK, you need to configure a few things.

Specify the license

The SDK requires a license to work, use the API license to specify a license key.

Dynamsoft.DDN.DocumentNormalizer.license = "YOUR-LICENSE-KEY";

To test the SDK, you can request a 30-day trial license via the Request a Trial License link.

Specify the location of the “engine” files

If the engine files (*.worker.js, *.wasm.js and *.wasm, etc.) are NOT in the same location with the main SDK file (ddn.js), you can use the API engineResourcePath to specify the engine path, for example:

// The following code uses the jsDelivr CDN, feel free to change it to your own location of these files.
Dynamsoft.DDN.DocumentNormalizer.engineResourcePath = "https://cdn.jsdelivr.net/npm/dynamsoft-document-normalizer@1.0.11/dist/";

Interact with the SDK

Create a DocumentNormalizer object

To use the SDK, we first create a DocumentNormalizer object.

Dynamsoft.DDN.DocumentNormalizer.license = "YOUR-LICENSE-KEY";
let normalizer = null;
try {
    normalizer = await Dynamsoft.DDN.DocumentNormalizer.createInstance();
} catch (ex) {
    console.error(ex);
}

Create a CameraEnhancer object and bind it to the DocumentNormalizer object

The CameraEnhancer object is necessary to access the camera to display the video stream and draw the found quads.

let cameraEnhancer = null;
cameraEnhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
let options = {
    resultsHighlightBaseShapes: Dynamsoft.DCE.DrawingItem
};
await normalizer.setImageSource(cameraEnhancer, options);

Change the camera settings (optional)

In some cases, a different camera might be required instead of the default one. Also, a different resolution might work better. To change the camera or the resolution, we use the CameraEnhancer object. Learn more here.

// The following lines set which camera and what resolution to use.
let allCameras = await cameraEnhancer.getAllCameras();
await cameraEnhancer.selectCamera(allCameras[0]);
await cameraEnhancer.setResolution(1280, 720);

Customize the DocumentNormalizer Settings (optional)

Check out the following code:

// Sets up the scanner behavior
let scanSettings = await normalizer.getScanSettings();
// Sets a scan interval in milliseconds so the SDK may release the CPU from time to time.
// (setting this value larger is a simple way to save battery power and reduce device heating).
scanSettings.intervalTime = 100; // The default is 0.
await normalizer.updateScanSettings(scanSettings);

// Sets up the runtime settings
let runtimeSettings = await normalizer.getRuntimeSettings();
runtimeSettings.ImageParameterArray[0].BinarizationModes[0].ThresholdCompensation = 3;
runtimeSettings.ImageParameterArray[0].ScaleDownThreshold = 512;
await normalizer.setRuntimeSettings(runtimeSettings);

// or uses a built-in runtime setting template "lowcontrast"
await normalizer.setRuntimeSettings("lowcontrast");

// Resets the runtime setting to default
await normalizer.resetRuntimeSettings();

As you can see from the above code snippets, there are two types of configurations:

  • get/updateScanSettings: Configures the scanning behavior of the normalizer which only includes intervalTime for now.

  • get/set/resetRuntimeSettings: Configures the normalizer engine with a built-in template or a template represented by a JSON object. This will override the previous RuntimeSettings.

Start the detection and normalization

After attaching an event handler to the event onQuadDetected. We can call startScanning(true) to start the detection process.

For user interaction, we should also add buttons for fucntions that invoke confirmQuadForNormalization() and normalizeWithConfirmedQuad().

// Triggered when a quadrilateral is detected from a video frame.
normalizer.onQuadDetected = (quadResults, sourceImage) => {
  console.log(quadResults);
};

// Click the button to pause the video and edit a quadrilateral.
document.getElementById('confirmQuadForNormalization').addEventListener("click", () => {
  normalizer.confirmQuadForNormalization();
});

// Click the button to normalize with the selected/adjusted quadrilateral.
document.getElementById('normalizeWithConfirmedQuad').addEventListener("click", async () => {
  const normalizedImageResult = await normalizer.normalizeWithConfirmedQuad();
  if(normalizedImageResult) {
    // Show the normalized image in a Canvas
    const cvs = normalizedImageResult.image.toCanvas();
    document.querySelector("#normalized-result").appendChild(cvs);
    console.log(normalizedImageResult);
  }
});
// Start scanning document boundaries.
await normalizer.startScanning(true);

Customize the UI (optional)

The built-in UI of the DocumentNormalizer object is defined in the file dist/ddn.ui.html . There are 4 ways to customize it:

  • Modify the file ddn.ui.html directly.

    This option is only possible when you host this file on your own web server instead of using a CDN. Note that this file is put in the dist directory of the dynamsoft-camera-enhancer package.

  • Copy the file ddn.ui.html to your application, modify it and pass its URL to the API setUIElement to set it as the default UI.

    await cameraEnhancer.setUIElement("THE-URL-TO-THE-FILE");

  • Append the default UI element to your page, customize it before showing it.

    <div id="camera-container"></div>

    document.getElementById('camera-container').appendChild(cameraEnhancer.getUIElement());
document.getElementsByClassName('dce-btn-close')[0].hidden = true; // Hide the close button

  • Build the UI element into your own web page and specify it with the API setUIElement(HTMLElement).

    • Embed the video

      <div id="div-ui-container" style="width:100%;height:100%;">
    <div class="dce-video-container" style="position:relative;width:100%;height:500px;"></div>
</div>
<script>
    (async () => {
        let cameraEnhancer = await Dynamsoft.DCE.CameraEnhancer.createInstance();
        let normalizer = await Dynamsoft.DDN.DocumentNormalizer.createInstance();
        let options = {
          resultsHighlightBaseShapes: Dynamsoft.DCE.DrawingItem
        };
        await normalizer.setImageSource(cameraEnhancer, options);

        await document.getElementById('div-ui-container').append(cameraEnhancer.getUIElement());
    })();
</script>

      The video element will be created and appended to the DIV element with the class dce-video-container , make sure the class name is the same. Also note that the CSS property position of the DIV element must be either relative , absolute , fixed , or sticky .

    • Add the camera list and resolution list

      If the class names for these lists match the default ones, dce-sel-camera and dce-sel-resolution , the SDK will automatically populate the lists and handle the camera/resolution switching.

      <div id="div-ui-container">
    <select class="dce-sel-camera"></select>
    <select class="dce-sel-resolution"></select>
    <br>
    <div class="dce-video-container" style="position:relative;width:100%;height:500px;"></div>
</div>

      By default, only 3 hard-coded resolutions (1920 x 1080, 1280 x 720, 640 x 480), are populated as options. You can show a customized set of options by hardcoding them.

      <select class="dce-sel-resolution">
    <option class="dce-opt-gotResolution" value="got"></option>
    <option data-width="1280" data-height="720">1280x720</option>
    <option data-width="1920" data-height="1080">1920x1080</option>
</select>

      Generally, you need to provide a resolution that the camera supports. However, in case a camera does not support the specified resolution, it usually uses the closest supported resolution. As a result, the selected resolution may not be the actual resolution. In this case, add an option with the class name dce-opt-gotResolution (as shown above) and the SDK will then use it to show the actual resolution.

API Documentation

You can check out the detailed documentation about the APIs of the SDK at https://www.dynamsoft.com/document-normalizer/docs/programming/javascript/api-reference/?ver=latest.

System Requirements

DDN-JS SDK requires the following features to work:

  • Secure context (HTTPS deployment)

    When deploying your application / website for production, make sure to serve it via a secure HTTPS connection. This is required for two reasons

    • Access to the camera video stream is only granted in a security context. Most browsers impose this restriction.

      Some browsers like Chrome may grant the access for http://127.0.0.1 and http://localhost or even for pages opened directly from the local disk (file:///...). This can be helpful for temporary development and test.

    • Dynamsoft License requires a secure context to work.

  • WebAssembly, Blob, URL/createObjectURL, Web Workers

    The above four features are required for the SDK to work.

  • MediaDevices/getUserMedia

    This API is only required for in-browser video streaming.

  • getSettings

    This API inspects the video input which is a MediaStreamTrack object about its constrainable properties.

The following table is a list of supported browsers based on the above requirements:

Browser Name Version
Chrome v85+ on desktop, v94+ on Android
Firefox v99+ on desktop and Android
Safari v15+ on iOS

Apart from the browsers, the operating systems may impose some limitations of their own that could restrict the use of the SDK.

Release Notes

Learn about what are included in each release at https://www.dynamsoft.com/document-normalizer/docs/programming/javascript/release-notes/?ver=latest.

Next Steps

Now that you have got the SDK integrated, you can choose to move forward in the following directions

  1. Check out the official samples.
  2. Learn about the available APIs.

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