There lots of great answers here which actually works. I just what to share the way I do this now with a more modern XML syntax, the constraint view. Trust me constraint view rooks!

<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#394BAB" tools:context="com.appdomain.app.apppro.ActivityName"> <ImageView android:id="@+id/nice_img" android:layout_width="fill_parent" android:layout_height="wrap_content" android:layout_marginTop="0dp" android:src="@drawable/green_square" android:scaleType="centerCrop" android:adjustViewBounds="true"