There are various XML attributes for ImageView to scale its content , and various layout views that allow to place views and set their sizes.
Howeve
Try using android:scaleType="fitCenter"
android:scaleType="fitCenter"
Edit
Hm, I saw what you mean, another option is to have it fitEnd on the portrait xml and create an identical xml on layout-land folder (create it if needed) with android:scaleType="fitCenter" which will be used on landscape only
fitEnd