How to convert an image to BLOB (bytes array) and vice-versa using Base64 encoder in your Android App? API 34 | Android 14

This video shows the steps to read an image file from the download folder of the android device. Then convert it into a Blob type, basically a bytes array. Then it encodes it into string type using Base64 character encoding. And it decodes it back.

It displays both encoded and decoded images in 2 separate ImageView widgets.

For API 34 | Android 14 version.

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Complete source code and other details:

package com.programmerworld.imagetoblob;

import static android.Manifest.permission.READ_MEDIA_IMAGES;

import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.os.storage.StorageManager;
import android.os.storage.StorageVolume;
import android.view.View;
import android.widget.ImageView;

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

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.Base64;

public class MainActivity extends AppCompatActivity {
    private ImageView imageView1, imageView2;

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

        ActivityCompat.requestPermissions(this,
                new String[]{READ_MEDIA_IMAGES},
                PackageManager.PERMISSION_GRANTED);

        imageView1 = findViewById(R.id.imageView1);
        imageView2 = findViewById(R.id.imageView2);
    }

    public void buttonImageToBlob(View view){
        StorageManager storageManager = (StorageManager) getSystemService(STORAGE_SERVICE);
        StorageVolume storageVolume = storageManager.getStorageVolumes().get(0);// 0 for internal storage
        // initial image
        Bitmap bitmap1 = BitmapFactory.decodeFile(storageVolume.getDirectory().getPath() + "/Download/flower.jpg");
        imageView1.setImageBitmap(bitmap1);

        // Encoding
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmap1.compress(Bitmap.CompressFormat.PNG, 0, byteArrayOutputStream);
        byte[] bytesImageEncoded = byteArrayOutputStream.toByteArray();
        String stringImageBytes = Base64.getEncoder().encodeToString(bytesImageEncoded);

        // Decoding
        byte[] bytesImageDecoded = Base64.getDecoder().decode(stringImageBytes);
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytesImageDecoded);
        Bitmap bitmap2 = BitmapFactory.decodeStream(byteArrayInputStream);
        imageView2.setImageBitmap(bitmap2);
    }
}

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

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

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.ImageToBlob"
        tools:targetApi="31">
        <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>

<?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">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="124dp"
        android:layout_marginTop="372dp"
        android:onClick="buttonImageToBlob"
        android:text="Convert to Blob"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="36dp"
        android:layout_marginTop="36dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/ic_launcher_background" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="44dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button"
        app:srcCompat="@drawable/ic_launcher_background" />

</androidx.constraintlayout.widget.ConstraintLayout>

Screenshots: