Android : ScrollView stretches background image
===

I would like to use the scrollview in a login form with a  background image but the image stretches. 

my code looks like the following :

     <ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
        android:layout_width="match_parent"
        android:layout_height="match_parent">
    
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center"
        android:orientation="vertical"
         android:id="@+id/login_layout" >
    
        <LinearLayout 
            android:layout_width="250dp"
            android:layout_height="270dp"
            android:layout_marginTop="40dp"
            android:gravity="center"
            android:orientation="vertical"
            android:background="@drawable/login" >
    
            <LinearLayout 
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginTop="30dp"
                android:orientation="vertical" >
    
     			<TextView 
     			  	android:layout_width="wrap_content"
                   	android:layout_height="wrap_content"
                   	android:text="@string/username_login" />
    	          	
             	<EditText
                   	android:id="@+id/username_login"
                   	android:inputType="text"
                   	android:layout_width="200dp"
                   	android:layout_height="30dp"
                   	android:paddingLeft="5dp"
                   	android:paddingTop="2dp"
                   	android:background="@drawable/edit_text" />
    
     			<TextView 
     			  	android:layout_width="wrap_content"
                   	android:layout_height="wrap_content"
                   	android:text="@string/password_login" />

            </LinearLayout>
            
        </LinearLayout>
    
    </LinearLayout>
    
    </ScrollView>


I have 2 text edits for username and password and a login button

any help please ?