Excluding ImageViews background from showing in LinearLayout

I want the ImageViews to be side-by-side (like android markets) with only the real image contents, without the background of its layout. How can i do this? please help

the xml code of the image views only:

     <TableRow
        android:id="@+id/tableRow2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:background="#afafafaf" >

        <HorizontalScrollView 
        android:layout_width="wrap_content"  
        android:layout_height="fill_parent">  

         <LinearLayout android:id="@+id/_linearLayout"  
             android:layout_width="wrap_content"  
             android:layout_height="wrap_content"  
            android:orientation="horizontal"
            android:gravity="center|left">  

            <ImageView android:id="@+id/_image"   
              android:layout_width="wrap_content"   
              android:layout_height="wrap_content"
              android:layout_gravity="left"
              android:background="#000000"
              android:src="@drawable/icon_2"/> 

               <ImageView android:id="@+id/_image"   
               android:layout_width="wrap_content"   
               android:layout_height="wrap_content"
               android:background="#000000"
               android:layout_gravity="left"
               android:src="@drawable/icon_2"/> 

            </LinearLayout>  

        </HorizontalScrollView>  

      </TableRow>