Dynamsoft Capture Vision for Node

This is a Node.js wrapper for Dynamsoft Capture Vision, enabling you to read barcodes, recognize partial label text, capture documents, and perform other advanced vision tasks.

Install SDK

npm i [email protected] -E

Getting Started

Take barcode reading from an image as an example.

const { LicenseManager, CaptureVisionRouter, EnumPresetTemplate } = require('dynamsoft-capture-vision-for-node');

// You can get your trial license from
// https://www.dynamsoft.com/customer/license/trialLicense -> Barcode Reader / Capture Vision Suite -> Desktop/Server/Embedded
// The current used license is valid for only one day.
LicenseManager.initLicense('DLS2eyJvcmdhbml6YXRpb25JRCI6IjIwMDAwMSJ9');

(async()=>{
  // you can get the image from https://github.com/Dynamsoft/capture-vision-nodejs-samples/blob/main/AllSupportedBarcodeTypes.png
  // The second parameter `templateName` tells the SDK how to process this image.
  let result = await CaptureVisionRouter.captureAsync('./AllSupportedBarcodeTypes.png', EnumPresetTemplate.PT_READ_BARCODES);
  // refer to https://www.dynamsoft.com/capture-vision/docs/server/programming/cplusplus/api-reference/capture-vision-router/auxiliary-classes/captured-result.html?product=dbr&lang=cplusplus
  // or run `console.log(require('node:util').inspect(result, false, null))` to see details
  for(let item of result.barcodeResultItems){
      console.log(item.text);
  }

  // Terminate workers so you can exit the process.
  // Don't call it if you still need to use the SDK.
  await CaptureVisionRouter.terminateIdleWorkers();
})();

If your trial license expired, please visit https://www.dynamsoft.com/customer/license/trialLicense -> Barcode Reader / Capture Vision Suite -> Desktop/Server.

Note

Guide for tasks such as Label Recognition and Document Capturing are under development. You can refer to the C++ document while writing code for Node.js. Or contact us for assistance.

Template Customization

The functionality of DCV largely depends on the choice of template. Dynamsoft offers preset templates. Below is an example illustrating how to modify the target barcode formats for a barcode reading task.

How to Specific the Barcode Formats

1. Copy SDK's Templates\DBR-PresetTemplates.json to your place. This file contains all the preset templates related to barcode reading.

2. Search BarcodeFormatIds and choose the one you need.

   e.g., If you only want to read specific barcode formats and ensure a high recognition rate, you can modify the BarcodeFormatIds object in the task-read-barcodes task.

3. Suppose you only want to recognize QRCode and DataMatrix, you can change BarcodeFormatIds like this. You can get barcode format strings here.

    "Name": "task-read-barcodes",
    "ExpectedBarcodesCount": 0,
    "BarcodeFormatIds": [
   -  "BF_DEFAULT"
   +  "BF_QR_CODE",
   +  "BF_DATAMATRIX"
    ],

4. Apply this template.

   CaptureVisionRouter.initSettings('path/to/the/template/file');

Warning

Due to its powerful customization capabilities, the number of configurable parameters in the templates is extensive and relatively complex. To ease your workload, if the preset templates do not meet your requirements, feel free to contact us for a customized template.

About the capture like API

captureAsync(...) process images in worker. The maximum number of workers is defined by CaptureVisionRouter.maxWorkerCount, which defaults to <logical processor number> - 1 (minimum of 1). If you continue to call captureAsync(...) while all workers are busy, the tasks will be queued and wait for execution. You can get the queue length by CaptureVisionRouter.waitQueueLength.

The synchronous version is capture(...), which processes images on the main thread.

The capture like APIs can accept file path string or file bytes Uint8Array as input data. Currently supported file types are jpg, png, bmp, gif, pdf. The capture like APIs also accept DCVImageData as input data. Typically used to process raw data from a camera.

interface DCVImageData{
  bytes: Uint8Array;
  width: number;
  height: number;
  stride: number;
  format: EnumImagePixelFormat;
  /** EXIF orientation; 1 or undefined means no rotate. */
  orientation?: number;
}

If input data is file bytes or DCVImageData, by default, captureAsync(...) will transfer bytes into worker. Thus you can't access to these bytes in main thread after captureAsync. This allows for optimal performance.

The following code can prevent bytes from being transferred.

let result = await CaptureVisionRouter.captureAsync(
  input_data_contains_bytes, {
    templateName: EnumPresetTemplate.XXXX,
    dataTransferType: 'copy'
  }
);

Supported OS/Arch

os	arch
win32 (windows)	x86, x64
linux	x64, arm64
darwin (mac)	x64, arm64

Caution

Since the Dynamsoft Capture Vision 2.6 version of .dylib is not compiled, the 2.4 version is used on the darwin platform, and the template and some other resources may be incompatible with linux/win32.

You can force(-f) install resources pkgs (dynamic libraries) for other OS/arch. So you can develop and deploy in different machines. You can check the <OS>-<arch>@<version> in this SDK's package.json->optionalDependencies.

npm i dynamsoft-capture-vision-for-node-lib-<OS>-<arch>@<version> -f -E

Samples

Web Service

Express sample and koa sample shows how to use the SDK in a web service.

You do not need to start multiple instance processes in PM2 Cluster mode. As mentioned above, Dynamsoft Capture Vision for Node already manages a thread pool. However, pm2 start app.js is still useful, it can automatically restart app.js when service crashes.

AWS Lambda

We also made special adaptation for AWS lambda, see this sample. Other similar single-function platforms may have some compatibility issues. If you have any needs, please contact us.

Special Notes

Character Model for Label Recognizer

When performing text recognition tasks，you need to install dynamsoft-capture-vision-for-node-charactermodel. You can check the <version> in SDK's package.json->peerDependencies.

npm i dynamsoft-capture-vision-for-node-charactermodel@<version> -E

Multiple CaptureVisionRouter Instances

In some rare cases you may need multiple CaptureVisionRouter instances, such as customizing different templates for each instance. Here is how to use:

let cvr = new CaptureVisionRouter();

let settings = cvr.outputSettings('<templateName>');
settings.foo = bar;
cvr.initSettings(settings);

let result = await cvr.captureAsync('<image>', '<templateName>');