Getting started with MRZ Scanner using Blink ID

Collins Swai — Thu, 21 Apr 2022 11:32:20 +0000

With the advancement in technology, various processes keep on being digitized. For example, we can obtain a traveler's information from national identity card or passport in the airports without having to key in every information.

With a scan on the MRZ section of the passport or national identity card, we can obtain information such as the traveler's name, nationality, age, document number, and even an image.

Introduction

This tutorial will build a simple Flutter application with BlinkId SDK to obtain user data from either a national ID or passport. With one quick scan, we will be able to extract information from identity cards, passports, driver licenses and virtually any other government-issued ID.

Introduction
Table of contents
Prerequisites
Application setup
MRZ scanning
Scan data user interface
- BlinkId account setup
Application testing
Conclusion

Prerequisites

In order to follow along, the reader will need the following:

Have Flutter SDK installed on your computer.
Background knowledge of Flutter.
A BlinkId account.

Application setup

On the command line, create a new directory to store our project files by executing the command below.

mkdir mrz

Change the working directory to the directory created above and execute the following command to create a new Flutter project.

cd mrz
flutter create --org com.mrzapp mrzapp

Once the project is created, open the project in your favourite IDE. In the root project directory, locate the pubspec.yaml file, and add the following dependencies in the dependency section.

  blinkid_flutter: ^5.13.0
  change_app_package_name: any

blinkid_flutter is the package that we will use to scan the MRZ section of the passport and national identity card to obtain the user data.
change_app_package_name is a package that we will use to change the package name of the application.

In the lib directory, add the following code snippet in the main.dart file.

class MRZApp extends StatelessWidget {
  const MRZApp({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter MRZ Scanner',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const ScanID(),
    );
  }
}

MRZ scanning

In the lib directory, create a new file named scan_screen.dart and add the following code snippet.
In the class created above, create a stateful Flutter widget named ScanID and add the following code snippet.

class ScanID extends StatefulWidget {
  const ScanID({Key? key}) : super(key: key);

  @override
  _ScanIDState createState() => _ScanIDState();
}

class _ScanIDState extends State<ScanID> {
  String? _resultString = "";
}

In the code snippet above, we created a stateful widget, and in its state class, we have a string _resultString that will store the scanned data.

In the _ScanIDState class, create a scan() method that will scan the MRZ section of the passport and national identity card. Update the scan() method with the following code snippet.

  Future<void> scan() async {
    String license;
    // Set the license key depending on the target platform you are building for.
    if (Theme.of(context).platform == TargetPlatform.iOS) {
      license =
          "";
    } else if (Theme.of(context).platform == TargetPlatform.android) {
      license =
          "";
    } else {
      license =
          "";
    }

    var idRecognizer = BlinkIdCombinedRecognizer();
    idRecognizer.returnFullDocumentImage = true;
    idRecognizer.returnFaceImage = true;

    BlinkIdOverlaySettings settings = BlinkIdOverlaySettings();

    var results = await MicroblinkScanner.scanWithCamera(
        RecognizerCollection([idRecognizer]), settings, license);

    if (!mounted) return;
    // When the scan is cancelled, the result is null therefore we return to the the main screen.
    if (results.isEmpty) return;
    //When the result is not null, we check if it is a passport then obtain the details using the `getPassportDetails` method and display them in the UI. If the document type is a national id, we get the details using the `getIdDetails` method and display them in the UI.
    for (var result in results) {
      if (result is BlinkIdCombinedRecognizerResult) {
        if (result.mrzResult?.documentType == MrtdDocumentType.Passport) {
          _resultString = getPassportResultString(result);
        } else {
          _resultString = getIdResultString(result);
        }

        setState(() {
          _resultString = _resultString;
          _fullDocumentFrontImageBase64 = result.fullDocumentFrontImage ?? "";
          _faceImageBase64 = result.faceImage ?? "";
        });

        return;
      }
    }
  }

In the code snippet above, we check the platform and provision the correct license key.
We then check if the camera is mounted, and if it is not, we return to the main screen. If the camera is mounted, we scan the document and obtain the result.

Replace the empty string with your license key, that you have obtained from BlinkId.

Until this point, we can scan a passport and a national ID using our application but cannot obtain the scan results. To obtain the scan results, we need to create methods named buildDriverLicenceResult, getIdResultString and getPassportResultString that will return the scan results in a string format. Then, add the following functions to the _ScanIDState class to get the scan results.

//This method is used to obtain the specific user details from the national id from the scan result object.
  String getIdResultString(BlinkIdCombinedRecognizerResult result) {
    // The information below will be otained from the natioal id if they are available.
    // In the case a field is not found, then it is skipped. For example, some national ids do not have the profession field.
    return buildResult(result.firstName, "First name") +
        buildResult(result.lastName, "Last name") +
        buildResult(result.fullName, "Full name") +
        buildResult(result.localizedName, "Localized name") +
        buildResult(result.additionalNameInformation, "Additional name info") +
        buildResult(result.address, "Address") +
        buildResult(
            result.additionalAddressInformation, "Additional address info") +
        buildResult(result.documentNumber, "Document number") +
        buildResult(
            result.documentAdditionalNumber, "Additional document number") +
        buildResult(result.sex, "Sex") +
        buildResult(result.issuingAuthority, "Issuing authority") +
        buildResult(result.nationality, "Nationality") +
        buildDateResult(result.dateOfBirth, "Date of birth") +
        buildIntResult(result.age, "Age") +
        buildDateResult(result.dateOfIssue, "Date of issue") +
        buildDateResult(result.dateOfExpiry, "Date of expiry") +
        buildResult(result.dateOfExpiryPermanent.toString(),
            "Date of expiry permanent") +
        buildResult(result.maritalStatus, "Martial status") +
        buildResult(result.personalIdNumber, "Personal Id Number") +
        buildResult(result.profession, "Profession") +
        buildResult(result.race, "Race") +
        buildResult(result.religion, "Religion") +
        buildResult(result.residentialStatus, "Residential Status") +
        buildDriverLicenceResult(result.driverLicenseDetailedInfo);
  }

  String buildResult(String? result, String propertyName) {
    if (result == null || result.isEmpty) {
      return "";
    }

    return propertyName + ": " + result + "\n";
  }
  //This function creates a complete date based on the date obtained from the scanned document. For example, date of the document issue.
  String buildDateResult(Date? result, String propertyName) {
    if (result == null || result.year == 0) {
      return "";
    }

    return buildResult(
        "${result.day}.${result.month}.${result.year}", propertyName);
  }

  String buildIntResult(int? result, String propertyName) {
    if (result == null || result < 0) {
      return "";
    }

    return buildResult(result.toString(), propertyName);
  }
  //This method obtained the 
  String buildDriverLicenceResult(DriverLicenseDetailedInfo? result) {
    if (result == null) {
      return "";
    }

    return buildResult(result.restrictions, "Restrictions") +
        buildResult(result.endorsements, "Endorsements") +
        buildResult(result.vehicleClass, "Vehicle class") +
        buildResult(result.conditions, "Conditions");
  }

  String getPassportResultString(BlinkIdCombinedRecognizerResult? result) {
    if (result == null) {
      return "";
    }

    var dateOfBirth = "";
    if (result.mrzResult?.dateOfBirth != null) {
      dateOfBirth = "Date of birth: ${result.mrzResult!.dateOfBirth?.day}."
          "${result.mrzResult!.dateOfBirth?.month}."
          "${result.mrzResult!.dateOfBirth?.year}\n";
    }

    var dateOfExpiry = "";
    if (result.mrzResult?.dateOfExpiry != null) {
      dateOfExpiry = "Date of expiry: ${result.mrzResult?.dateOfExpiry?.day}."
          "${result.mrzResult?.dateOfExpiry?.month}."
          "${result.mrzResult?.dateOfExpiry?.year}\n";
    }

    return "First name: ${result.mrzResult?.secondaryId}\n"
        "Last name: ${result.mrzResult?.primaryId}\n"
        "Document number: ${result.mrzResult?.documentNumber}\n"
        "Sex: ${result.mrzResult?.gender}\n"
        "$dateOfBirth"
        "$dateOfExpiry";
  }
  // This widget will display a complete image of the scanned passport or national id.

The buildDriverLicenceResult method is used to obtain the driver licence details from the scan result object when a driver licence is scanned.
The getIdResultString method is used to obtain the user details from the scanned national ID.
The buildResult method is used to obtain the specific date from the scanned document, i.e. date of birth, date of issue, date of expiry, etc.

Scan data user interface

Then, we need to display the data obtained from the scan in the user interface. Therefore, we need to add the following widgets to the _ScanIDState class.

  // This widget will display a complete image of the passport or national id that is scanned.
  @override
  Widget build(BuildContext context) {
    Widget fullDocumentFrontImage = Container();
    if (_fullDocumentFrontImageBase64 != null &&
        _fullDocumentFrontImageBase64 != "") {
      fullDocumentFrontImage = Column(
        children: <Widget>[
          const Text("Document Front Image:"),
          Image.memory(
            const Base64Decoder().convert(_fullDocumentFrontImageBase64!),
            height: 180,
            width: 350,
          )
        ],
      );
    }
    //This widget will show the user image obtained from the passport or national id
    Widget faceImage = Container();
    if (_faceImageBase64 != null && _faceImageBase64 != "") {
      faceImage = Column(
        children: <Widget>[
          const Text("Face Image:"),
          Image.memory(
            const Base64Decoder().convert(_faceImageBase64!),
            height: 150,
            width: 100,
          )
        ],
      );
    }

    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          automaticallyImplyLeading: true,
          centerTitle: true,
          title: const Text(
            "Scan ID for Visitor",
            style: TextStyle(color: Colors.white),
          ),
        ),
        body: SingleChildScrollView(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            children: <Widget>[
              Padding(
                  child: ElevatedButton(
                    child: const Text("Scan ID"),
                    onPressed: () => scan(),
                  ),
                  padding: const EdgeInsets.only(bottom: 16.0)),
              Text(_resultString!),
              fullDocumentFrontImage,
              // fullDocumentBackImage,
              faceImage,
            ],
          ),
        ),
      ),
    );
  }

The scan() method starts the camera application when scanning the passport or national ID. When the scan is completed, the getIdResultString() method is invoked to decode the result from the scan() method and display it on the screen.
When the scan is completed, the getPassportResultString() method is invoked to decode the result from the scan() method and display it on the screen.

BlinkId account setup

Navigate to microblink.com and create a new account.
Copy the license key from the settings page of your BlinkID account and replace the licenseKey variable with the license key in the scan() method.

Application testing

We have completed developing our application. We need to test it to ensure everything works as expected. Therefore, we need to execute the following command in the project root directory to run the application on an Android phone.

flutter run android --target-platform android-arm

Conclusion

Now that you have learned how to set up and use the BlinkId SDK in a Flutter application, you can start using the SDK in your applications. You can download the complete source code for the application here.

Happy coding!

DEV Community: Collins Swai