remove white background of image in android

I added an innerimage inside a framelayout in android.But the thing is that i am getting a white colour background.I need to remove that white colour Background.Any help will be appreciated.....

Screenshot is given below

xml file is given below

<?xml version="1.0" encoding="UTF-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <ImageView  
        android:id="@+id/imageView"
        android:layout_width="fill_parent" 
        android:layout_height="fill_parent" 
        android:scaleType="center"
         />

    <ImageView
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_gravity="left"
        android:background="@null"
        android:maxWidth="-5dp"  
        android:maxHeight="-5dp"
        android:src="@drawable/driveimg"
         />

</FrameLayout>

you can either set the background to null (android:background="@null") or use a transparent color (android:background="@android:color/transparent")