How can I stretch the image in imagebutton to the whole area of the imagebutton?

Here is a picture that will help you understand my problem:

I want to stretch the image shown inside ImageButton to the whole area of the ImageButton. As you can see, the picture with the number 1 only take about 95% of the ImageButton and you can also see the boundaries of the ImageButton.

I still want to maintain the image button style

Here's how I am using ImageView:

<ImageButton
    android:id="@+id/secondActivityBbuttonDownRight"
    android:layout_width="0dip"
    android:layout_height="match_parent"
    android:layout_weight="0.5"
    android:scaleType="fitStart"
    android:src="@drawable/111" />

I think I found out what is my problem. I need a custom component that can contain only an image and have a clicking effect.