How to read texts from an image (OCR) using google vision library in your Android App?

This video shows the steps to implement the google vision library to read or detect the texts and strings from an image, like an OCR (Optical Character Recognition). It demonstrates the functionality using different fonts and text sizes in the different images.

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Complete source code

package com.programmerworld.imagetotextapp;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import android.Manifest;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.util.SparseArray;
import android.view.View;
import android.widget.EditText;
import android.widget.ImageView;
import android.widget.TextView;

import com.google.android.gms.vision.Frame;
import com.google.android.gms.vision.text.TextBlock;
import com.google.android.gms.vision.text.TextRecognizer;

public class MainActivity extends AppCompatActivity {

    private TextView textView;
    private EditText editText;
    private ImageView imageView;
    private Bitmap bitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.READ_EXTERNAL_STORAGE,
                Manifest.permission.WRITE_EXTERNAL_STORAGE},
                PackageManager.PERMISSION_GRANTED);

        textView = findViewById(R.id.textView);
        editText = findViewById(R.id.editText);
        imageView = findViewById(R.id.imageView);
    }

    public void buttonReadText(View view){
        try {
            String stringFileName = "/storage/emulated/0/Download/" + editText.getText().toString();
            bitmap = BitmapFactory.decodeFile(stringFileName);
            imageView.setImageBitmap(bitmap);
            TextRecognizer textRecognizer = new TextRecognizer.Builder(this).build();
            Frame frameImage = new Frame.Builder().setBitmap(bitmap).build();
            SparseArray<TextBlock> textBlockSparseArray = textRecognizer.detect(frameImage);
            String stringImageText = "";
            for (int i = 0; i<textBlockSparseArray.size();i++){
                TextBlock textBlock = textBlockSparseArray.get(textBlockSparseArray.keyAt(i));
                stringImageText = stringImageText + " " + textBlock.getValue();
            }
            textView.setText(stringImageText);
        }
        catch (Exception e){
            textView.setText("Failed");
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.programmerworld.imagetotextapp">

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

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ImageToTextApp">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

plugins {
    id 'com.android.application'
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.programmerworld.imagetotextapp"
        minSdk 31
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.4.1'
    implementation 'com.google.android.material:material:1.5.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.3'
    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

    implementation 'com.google.android.gms:play-services-vision:20.1.3'
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.362" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="153dp"
        android:layout_marginTop="141dp"
        android:onClick="buttonReadText"
        android:text="Read Text"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <EditText
        android:id="@+id/editText"
        android:layout_width="227dp"
        android:layout_height="64dp"
        android:layout_marginStart="100dp"
        android:layout_marginTop="40dp"
        android:ems="10"
        android:inputType="textPersonName"
        android:text="images.jpeg"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="249dp"
        android:layout_height="271dp"
        android:layout_marginStart="85dp"
        android:layout_marginTop="51dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView"
        app:srcCompat="@drawable/ic_launcher_background" />

</androidx.constraintlayout.widget.ConstraintLayout>