For these ImageButtons set the images using (instead of src):
Next thing is set:
android:layout_height="10dp" //or any size required android:layout_width="10dp" //or any size required ... let these 2 sizes be same for both the ImageButtons
“dp” or “dip” is device independent pixels. The android system will take care of the resizing for different screen resolutions
Also, a better thing to do would be to set-up hover images for your button separately.