This video shows the steps to compress the image size and save it as another file in the download folder from your Android App.

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Complete source code and other details:

package com.programmerworld.compressmyimage;

import static android.Manifest.permission.READ_MEDIA_IMAGES;
import static android.Manifest.permission.WRITE_EXTERNAL_STORAGE;

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

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 java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {
    private ImageView imageView, imageView2;
    private StorageVolume storageVolume;
    private Bitmap bitmapImage;

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

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

        imageView = findViewById(R.id.imageView);
        imageView2 = findViewById(R.id.imageView2);

        StorageManager storageManager = (StorageManager) getSystemService(STORAGE_SERVICE);
        storageVolume = storageManager.getStorageVolumes().get(0); // internal storage
        File fileInput = new File(storageVolume.getDirectory().getPath() + "/Download/images.jpeg");
        bitmapImage = BitmapFactory.decodeFile(fileInput.getPath());

        imageView.setImageBitmap(bitmapImage);
    }

    public void buttonCompressImage(View view) throws IOException {
        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
        bitmapImage.compress(Bitmap.CompressFormat.JPEG, 0, byteArrayOutputStream);
        byte[] bytesArray = byteArrayOutputStream.toByteArray();
        Bitmap bitmapCompressedImage = BitmapFactory.decodeByteArray(bytesArray, 0, bytesArray.length);
        imageView2.setImageBitmap(bitmapCompressedImage);

        File fileOutput = new File(storageVolume.getDirectory().getPath() + "/Download/output1.jpeg");
        FileOutputStream fileOutputStream = new FileOutputStream(fileOutput);
        fileOutputStream.write(bytesArray);
        fileOutputStream.close();
    }
}

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

    <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:supportsRtl="true"
        android:theme="@style/Theme.CompressMyImage"
        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="114dp"
        android:layout_marginTop="47dp"
        android:onClick="buttonCompressImage"
        android:text="Compress Image"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="180dp"
        android:layout_height="165dp"
        android:layout_marginStart="112dp"
        android:layout_marginTop="68dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button"
        app:srcCompat="@drawable/ic_launcher_background" />

    <ImageView
        android:id="@+id/imageView2"
        android:layout_width="180dp"
        android:layout_height="165dp"
        android:layout_marginStart="96dp"
        android:layout_marginTop="88dp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView"
        app:srcCompat="@drawable/ic_launcher_background" />

</androidx.constraintlayout.widget.ConstraintLayout>