Android怎样才能只在半屏上应用相机效果？

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

<SurfaceView
    android:id="@+id/surfaceView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

private SurfaceView surfaceView;
private Camera camera;

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

    surfaceView = findViewById(R.id.surfaceView);
}

@Override
protected void onResume() {
    super.onResume();
    initializeCamera();
}

@Override
protected void onPause() {
    super.onPause();
    releaseCamera();
}

private void initializeCamera() {
    camera = Camera.open();
    Camera.Parameters parameters = camera.getParameters();

    // 设置相机参数，如预览尺寸等

    // 计算半屏尺寸
    DisplayMetrics displayMetrics = new DisplayMetrics();
    getWindowManager().getDefaultDisplay().getMetrics(displayMetrics);
    int screenWidth = displayMetrics.widthPixels;
    int screenHeight = displayMetrics.heightPixels;
    int halfScreenWidth = screenWidth / 2;
    int halfScreenHeight = screenHeight / 2;

    // 设置预览尺寸为半屏尺寸
    parameters.setPreviewSize(halfScreenWidth, halfScreenHeight);

    // 调整预览方向
    camera.setDisplayOrientation(90);

    // 将相机预览与SurfaceView关联
    try {
        camera.setPreviewDisplay(surfaceView.getHolder());
    } catch (IOException e) {
        e.printStackTrace();
    }

    // 开始预览
    camera.startPreview();
}

private void releaseCamera() {
    if (camera != null) {
        camera.stopPreview();
        camera.release();
        camera = null;
    }
}