How to Encrypt and Decrypt Images in Android?

package org.geeksforgeeks.demo;

import android.content.ContextWrapper;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.Nullable;
import androidx.appcompat.app.AppCompatActivity;

import com.bumptech.glide.Glide;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.security.InvalidKeyException;

import javax.crypto.Cipher;
import javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import javax.crypto.spec.SecretKeySpec;

public class MainActivity extends AppCompatActivity {

    private ImageView imageView;
    private Button encBtn;
    private Button decBtn;

    // AES encryption key - must be 16, 24, or 32 bytes in length for AES-128, AES-192, or AES-256 respectively
    private final String secretKey = "MySecretKey12345";

    // Registering an image picker activity to allow the user to select an image from device storage
    private final ActivityResultLauncher<String> imagePickerLauncher =
            registerForActivityResult(new ActivityResultContracts.GetContent(), this::onImagePicked);

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

        // Initialize views
        imageView = findViewById(R.id.imageView);
        encBtn = findViewById(R.id.encryptButton);
        decBtn = findViewById(R.id.decryptButton);

        // Set click listener for encrypt button
        encBtn.setOnClickListener(v -> {
            // Launch image picker to select image for encryption
            imagePickerLauncher.launch("image/*");
        });

        // Set click listener for decrypt button
        decBtn.setOnClickListener(v -> {
            try {
                // Attempt to decrypt and display the image
                decrypt();
            } catch (Exception e) {
                e.printStackTrace();
                Toast.makeText(this, "Decryption failed", Toast.LENGTH_SHORT).show();
            }
        });
    }

    // Callback when an image is picked
    private void onImagePicked(Uri uri) {
        if (uri != null) {
            try {
                // Get input stream of the selected image
                InputStream inputStream = getContentResolver().openInputStream(uri);

                // Encrypt the image using the input stream
                encrypt(inputStream);

                Toast.makeText(this, "Image encrypted.", Toast.LENGTH_SHORT).show();
            } catch (Exception e) {
                e.printStackTrace();
                Toast.makeText(this, "Encryption failed: " + e.getMessage(), Toast.LENGTH_SHORT).show();
            }
        }
    }

    // Returns a directory where encrypted/decrypted images will be stored
    private File getPhotoDirectory() {
        ContextWrapper contextWrapper = new ContextWrapper(this);
        return contextWrapper.getExternalFilesDir(Environment.DIRECTORY_DCIM);
    }

    // Returns file reference for the encrypted image
    private File getEncryptedFile() {
        return new File(getPhotoDirectory(), "encfile.png");
    }

    // Returns file reference for the decrypted image
    private File getDecryptedFile() {
        return new File(getPhotoDirectory(), "decfile.png");
    }

    // Encrypts the image from the input stream using AES encryption
    private void encrypt(InputStream inputStream) throws Exception {
        File encryptedFile = getEncryptedFile();

        // Create AES key specification
        SecretKeySpec sks = new SecretKeySpec(secretKey.getBytes(), "AES");

        // Initialize cipher in encrypt mode
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.ENCRYPT_MODE, sks);

        // Write encrypted data to file
        try (CipherOutputStream cos = new CipherOutputStream(new FileOutputStream(encryptedFile), cipher)) {
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                cos.write(buffer, 0, bytesRead);
            }
        } finally {
            inputStream.close();
        }
    }

    // Decrypts the previously encrypted image file and displays it in the ImageView
    private void decrypt() throws Exception {
        File encryptedFile = getEncryptedFile();
        File decryptedFile = getDecryptedFile();

        // Create AES key specification
        SecretKeySpec sks = new SecretKeySpec(secretKey.getBytes(), "AES");

        // Initialize cipher in decrypt mode
        Cipher cipher = Cipher.getInstance("AES");
        cipher.init(Cipher.DECRYPT_MODE, sks);

        // Decrypt data and write it to the decrypted file
        try (
            CipherInputStream cis = new CipherInputStream(new FileInputStream(encryptedFile), cipher);
            FileOutputStream fos = new FileOutputStream(decryptedFile)
        ) {
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = cis.read(buffer)) != -1) {
                fos.write(buffer, 0, bytesRead);
            }
        }

        // Load and display the decrypted image if it exists
        if (decryptedFile.exists()) {
            Bitmap bitmap = BitmapFactory.decodeFile(decryptedFile.getAbsolutePath());

            // Load bitmap into ImageView using Glide
            Glide.with(this).load(bitmap).into(imageView);

            Toast.makeText(this, "Decryption successful", Toast.LENGTH_SHORT).show();
        }
    }
}