DOT Android Document library

v3.7.2

Introduction

DOT Android Document provides components for document capture and related functionalities which are easy to integrate into an Android application.

Requirements

DOT Android Document has the following requirements:

Minimum Android API level 21
Minimum Kotlin Gradle plugin version 1.6.0 (if used)

Distribution

Maven Repository

DOT Android Document is distributed as an Android library (.aar package) stored in the Innovatrics maven repository.

In order to integrate DOT Android Document into your project, the first step is to include the Innovatrics maven repository and Google repository to your top level build.gradle file.

build.gradle

allprojects {
    repositories {
        google()
        maven {
            url 'https://maven.innovatrics.com/releases'
        }
    }
}

Then, specify the dependency on DOT Android Document library in the module’s build.gradle file. Dependencies of this library will be downloaded alongside the library.

build.gradle

dependencies {
    //…
    implementation "com.innovatrics.dot:dot-document:$dotDocumentVersion"
    //…
}

Supported Architectures

DOT Android Document provides binaries for these architectures:

armeabi-v7a
arm64-v8a
x86
x86_64

If your target application format is APK and not Android App Bundle, and the APK splits are not specified, the generated APK file will contain binaries for all available architectures. Therefore we recommend to use APK splits. For example, to generate arm64-v8a APK, add the following section into your module build.gradle:

build.gradle

splits {
    abi {
        enable true
        reset()
        include 'arm64-v8a'
        universalApk false
    }
}

If you do not specify this section, the resulting application can become too large in size.

Permissions

DOT Android Document declares the following permission in AndroidManifest.xml:

AndroidManifest.xml

<uses-permission android:name="android.permission.CAMERA" />

Basic Setup

Logging

Although logging is disabled by default, it can be enabled explicitly by using the following method from the com.innovatrics.dot.core.Logger class.

Logger.setLoggingEnabled(true);

The appropriate place for this call is within the onCreate() method of your subclass of android.app.Application. Each TAG of a log message starts with the prefix dot-document:.

This setting enables logging for all DOT Android libraries.

Keep in mind that logging should be used just for debug purposes as it might produce a lot of log messages.

Components

Overview

DOT Android Document provides both non-UI and UI components. Non-UI components are aimed to be used by developers who want to build their own UI using the DOT Android Document functionality. UI components are build on top of non-UI components. These are available as abstract fragments and can be extended and then embedded into the application’s existing activity providing more control.

List of Non-UI Components

DOCUMENT DETECTOR: A component for performing document detection on an image.
IMAGE PARAMETERS ANALYZER: A component for computing image parameters such as sharpness, brightness or hotspots score.
IMAGE PERSPECTIVE WARPER: A component for perspective warping an image according detected document card corners.
DOCUMENT AUTO CAPTURE CONTROLLER: A component for capturing good quality images suitable for optical character recognition.
MACHINE READABLE ZONE READER: A component for reading Machine Readable Zone (MRZ).

List of UI Components

DOCUMENT AUTO CAPTURE: A visual component for capturing good quality images suitable for optical character recognition.

Non-UI Components

Document Detector

The DocumentDetector interface provides a document detection functionality.

Create a DocumentDetector:

DocumentDetector documentDetector = DocumentDetectorFactory.create();

To perform detection, call the following method on the background thread:

DocumentDetector.Result result = documentDetector.detect(bgraRawImage);

Image Parameters Analyzer

The ImageParametersAnalyzer interface provides an image parameters analysis functionality.

Create ImageParametersAnalyzer:

ImageParametersAnalyzer imageParametersAnalyzer = ImageParametersAnalyzerFactory.create();

To perform analysis, call the following method on the background thread:

ImageParameters imageParameters = imageParametersAnalyzer.analyze(bgraRawImage);

Image Perspective Warper

The ImagePerspectiveWarper interface provides perspective warping functionality.

Create ImagePerspectiveWarper:

ImagePerspectiveWarper imagePerspectiveWarper = ImagePerspectiveWarperFactory.create();

To perform perspective warping, call the following method on the background thread:

BgraRawImage warpedBgraRawImage = imagePerspectiveWarper.warp(bgraRawImage, corners, targetImageSize);

Document Auto Capture Controller

The DocumentAutoCaptureController interface provides a stateful document auto capture functionality.

Create DocumentAutoCaptureController:

DocumentAutoCaptureControllerConfiguration configuration = new DocumentAutoCaptureControllerConfiguration.Builder(context, validators)
    .detectionNormalizedRectangle(detectionNormalizedRectangle)
    .imageParametersNormalizedRectangle(imageParametersNormalizedRectangle)
    .onDetectionListener(this::handleDetection)
    .onCandidateSelectionStartListener(this::handleCandidateSelectionStart)
    .onCaptureListener(this::handleCapture)
    .build();
DocumentAutoCaptureController documentAutoCaptureController = DocumentAutoCaptureControllerFactory.create(configuration);

`DocumentAutoCaptureControllerConfiguration.Builder` arguments

(Required) [-] Context context - Android context.
(Required) [-] List<DocumentAutoCaptureDetectionValidator> validators - List of validators. Validations are applied in the same order in which they are stored in the list.
(Optional) [2] int minValidFramesInRowToStartCandidateSelection - Minimum number of valid frames in a row to start candidate selection.
(Optional) [1000] int candidateSelectionDurationMillis - Duration of candidate selection in milliseconds.
(Optional) [-] RectangleDouble detectionNormalizedRectangle - Crop an input image to normalized detection rectangle and use that for document detection.
(Optional) [-] RectangleDouble imageParametersNormalizedRectangle - Crop an input image to normalized image parameters rectangle and use that to analyze image parameters.
(Optional) [false] boolean mrzReadingEnabled - If Machine Readable Zone reading is enabled.
(Optional) [-] DocumentAutoCaptureController.OnDetectionListener onDetectionListener - Listener to be called on each document detection periodically.
(Optional) [-] DocumentAutoCaptureController.OnCandidateSelectionStartListener onCandidateSelectionStartListener - Listener to be called when candidate selection is started. This event happens once in a auto capture process.
(Optional) [-] DocumentAutoCaptureController.OnCaptureListener onCaptureListener - Listener to be called on auto capture process is done.

In order to get callbacks from the controller, implement these listeners from DocumentAutoCaptureController interface: OnDetectionListener, OnCandidateSelectionStartListener and OnCaptureListener.

You can use detectionNormalizedRectangle to specify the region in the input image which will be used for document detection. For example, if you want to ignore top 30% and bottom 30% of the input image, you can do it as follows:

RectangleDouble detectionNormalizedRectangle = RectangleDouble.of(0.0d, 0.3d, 1.0d, 0.7d);

If detectionNormalizedRectangle is not specified, the source input image is used for document detection.

You can use imageParametersNormalizedRectangle to specify the region in the input image which will be used to analyze image parameters. For example, if you want to ignore top 35%, left 5%, right 5% and bottom 35% of the input image, you can do it as follows:

RectangleDouble imageParametersNormalizedRectangle = RectangleDouble.of(0.05d, 0.35d, 0.95d, 0.65d);

If imageParametersNormalizedRectangle is not specified, the source input image is used to analyze image parameters.

To capture a good quality document image, repeatedly call the process() method using the camera frames:

documentAutoCaptureController.process(bgraRawImage);

The controller evaluates the document image requirements for each frame. Once there are minValidFramesInRowToStartCandidateSelection valid frames in a row, candidate selection is started with duration of candidateSelectionDurationMillis milliseconds. After the candidate selection is finished, the best document image candidate is returned by the OnCaptureListener and the document auto capture process is over.

In case you want to force the capture event, call the requestCapture() method. After you call the next process() method, the input image will be returned as a result by the OnCaptureListener and the document auto capture process will be finished.

documentAutoCaptureController.requestCapture();

In case you want to restart the document auto capture process, call the restart() method.

documentAutoCaptureController.restart();

Machine Readable Zone Reader

The MrzReader interface provides a Machine Readable Zone (MRZ) reading functionality.

Create MrzReader:

MrzReaderConfiguration configuration = new MrzReaderConfiguration.Builder(context).build();
MrzReader mrzReader = MrzReaderFactory.create(configuration);

To read a MRZ, call the following method on the background thread:

MrzReader.Result result = mrzReader.read(bgraRawImage, documentDetectorResult);

Or, alternatively if you know the travel document type call this method to order to increase precision of reading:

MrzReader.Result result = mrzReader.read(bgraRawImage, documentDetectorResult, travelDocumentType);

Argument documentDetectorResult is a product of either Document Detector component, Document Auto Capture Controller component or Document Auto Capture UI component.

The result of successful MRZ reading contains travel document type and machine readable zone. If MRZ reading was not successful, the result will contain an exception and travelDocumentType and/or machineReadableZone may be null.

UI Components

Orientation Change

In order to handle the orientation change in multi-window mode correctly, configure the activity in your AndroidManifest.xml file as follows:

<activity
    android:name=".MyActivity"
    android:configChanges="screenSize|smallestScreenSize|screenLayout|orientation" />

Document Auto Capture

The fragment with a document placeholder on the screen. The component is embedded into the application as a fragment from Android Support Library. The fragment is abstract, so it must be subclassed. In order to configure the behavior of DocumentAutoCaptureFragment, use DocumentAutoCaptureConfiguration:

DocumentAutoCaptureConfiguration documentAutoCaptureConfiguration = new DocumentAutoCaptureConfiguration.Builder().build();

Bundle arguments = new Bundle();
arguments.putSerializable(DocumentAutoCaptureFragment.CONFIGURATION, documentAutoCaptureConfiguration);

Fragment fragment = new DemoDocumentAutoCaptureFragment();
fragment.setArguments(arguments);

getSupportFragmentManager()
    .beginTransaction()
    .replace(android.R.id.content, fragment)
    .commit();

The following arguments are wrapped in DocumentAutoCaptureConfiguration:

(Optional) [CameraFacing.BACK] CameraFacing cameraFacing - Camera facing.
- CameraFacing.FRONT
- CameraFacing.BACK
(Optional) [CameraPreviewScaleType.FIT] CameraPreviewScaleType cameraPreviewScaleType - The camera preview scale type.
- CameraPreviewScaleType.FIT
- CameraPreviewScaleType.FILL
(Optional) [ValidationMode.STANDARD] ValidationMode validationMode - Validation mode.
- ValidationMode.STANDARD
- ValidationMode.STRICT
(Optional) [0.900d] double confidenceLowThreshold - Low detection confidence threshold.
(Optional) [0.430d] double sizeSmallThreshold - Small size threshold.
(Optional) [0.650d] double sharpnessLowThreshold - Low sharpness threshold.
(Optional) [0.250d] double brightnessLowThreshold - Low brightness threshold.
(Optional) [0.900d] double brightnessHighThreshold - High brightness threshold.
(Optional) [0.008d] double hotspotsScoreHighThreshold - High hotspots score threshold.
(Optional) [false] boolean detectionLayerVisible - If detection UI layer (tracking rectangle) is visible.
(Optional) [false] boolean mrzReadingEnabled - If Machine Readable Zone reading is enabled.

As soon as the fragment is created, the camera preview starts. To start the auto capture process call the start() method. You can start the process any time.

In case you want to handle detection data, implement onDetected() callback. This callback is called with each processed camera frame. There is also onCandidateSelectionStarted() callback, which is called only once for the whole process, when candidate selection is started.

In case you want to force the capture event, call the requestCapture() method. Document image candidate will be returned via the onCaptured() callback asynchronously.

In case you want to restart the auto capture process (e.g. you want to capture both sides of the document, one after another), call the restart() method. The whole process will start from the beginning.

Customization of UI components

Strings

You can override the string resources in your application and provide alternative strings for supported languages using the standard Android localization mechanism.

<!-- Document Auto Capture -->
<string name="dot_document_auto_capture_instruction_brightness_too_high">Less light needed</string>
<string name="dot_document_auto_capture_instruction_brightness_too_low">More light needed</string>
<string name="dot_document_auto_capture_instruction_candidate_selection">Hold still…</string>
<string name="dot_document_auto_capture_instruction_document_centering">Center document</string>
<string name="dot_document_auto_capture_instruction_document_not_present">Scan document</string>
<string name="dot_document_auto_capture_instruction_document_too_far">Move closer</string>
<string name="dot_document_auto_capture_instruction_hotspots_present">Avoid reflections</string>
<string name="dot_document_auto_capture_instruction_mrz_not_valid">Scan valid machine readable document</string>
<string name="dot_document_auto_capture_instruction_sharpness_too_low">More light needed</string>

Colors

You may customize the colors used by DOT Android Document in your application. To use custom colors, override the specific color.

<color name="dot_detection_layer">#ffffffff</color>
<color name="dot_instruction_background">#fff8fbfb</color>
<color name="dot_instruction_candidate_selection_background">#ff00bfb2</color>
<color name="dot_instruction_text">#ff131313</color>
<color name="dot_placeholder">#ffffffff</color>
<color name="dot_placeholder_candidate_selection">#ff00bfb2</color>
<color name="dot_placeholder_overlay">#80131313</color>

Styles

Text views and buttons can be styled by overriding the parent style in the application.

<style name="TextAppearance.Dot.Medium" parent="TextAppearance.AppCompat.Medium" />
<style name="TextAppearance.Dot.Medium.Instruction" />

Common Classes

`ImageSize`

DTO which represents a size of an image. To create an instance:

ImageSize imageSize = ImageSize.of(width, height);

`BgraRawImage`

DTO which represents and an image. To create an instance:

BgraRawImage bgraRawImage = BgraRawImage.of(size, bytes);

To create an instance from Bitmap:

BgraRawImage bgraRawImage = BgraRawImageFactory.create(bitmap);

`Corners`

DTO which represents a document card corners. To create an instance:

Corners corners = Corners.of(topLeft, topRight, bottomRight, bottomLeft);

Stability issue in image conversion.

DOT Android Document library

v3.7.2#

v3.7.2