how to set a bitmap in a shape in xml

I 'm using this for a LinearLayout's selector

normal.xml:

<?xml version="1.0" encoding="UTF-8"?> 
<shape xmlns:android="http://ift.tt/nIICcg"> 
<solid android:color="#FFFFFF"/>    
</shape>

pressed.xml

<?xml version="1.0" encoding="UTF-8"?> 
<shape xmlns:android="http://ift.tt/nIICcg"> 
<solid android:color="#F89E1C"/>      
</shape>

selector

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://ift.tt/nIICcg">
<item android:state_pressed="true" android:drawable="@drawable/pressed" />
<item  android:state_focused="false" android:drawable="@drawable/normal" />
</selector>

how can I set a bitmap in the pressed.xml instead of a color?