What's the right and clean way to handle images aspect ratio?

In my app, if I rotate the screen, I lose the aspect ratio and my images appear ugly as hell
- see these images comparing my app and Play Store - <http://imgur.com/a/GriwP#0> 

This is how I'm doing:

```
<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    android:layout_gravity="center" >

    <Button
        android:id="@+id/btnStark"
        android:layout_marginLeft="4dp"
        android:layout_marginRight="2dp"
        android:layout_width="fill_parent"
        android:layout_height="100dp"
        android:layout_weight="1"
        android:background="@drawable/stark"
        android:gravity="center|bottom"
        android:layout_gravity="top" />

    <Button
        android:id="@+id/btnLannister"
        android:layout_marginLeft="2dp"
        android:layout_marginRight="4dp"
        android:layout_width="fill_parent"
        android:layout_height="100dp"
        android:layout_weight="1"
        android:background="@drawable/stark"
        android:gravity="center|bottom"
        android:layout_gravity="top" />
</LinearLayout>

```

How should I handle the height? Should I set a fixed value? Or is there any way it automatically keeps the aspect ratio?

The image I'm using is 400x300 pixels