Android :: Change Vertical Horizontal Rate - Circle Becomes Ellipse

I want horizontal-vertical rate unchanged. How can ı Do this?? my picture is rate is 320x70. for example, in my phone(samsung galaxy-s GT-I9000) it looks like 320x100. originally I have a circle but it look ellipse... ı have to fix it, but how can ı do?

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:background="@drawable/main"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/resandroid">
<LinearLayout android:layout_width="fill_parent" android:layout_height="fill_parent"
android:orientation="vertical" android:layout_weight="5"></LinearLayout>.........................