Hello, i just made my first app, images looks fine on the game player bad when i export it to android/windows phone images quality is low.
image from player
images from android/windows phone
Go to Edit > Project Settings > Quality and (1) click ‘Add Quality Level’. Then select it in the list of presets and (2) rename it to something like “MyQualitySettings”. Next, make sure (3) texture quality is set to Full Res, and (4) click the arrow below the Android column and enable “MyQualitySettings” (the green checkbox in the Android column should change to your setting).
Next, bring the sprite up in the inspector window and click on the Android settings. Check to make sure ‘Override for Android’ is disabled.
Let me know if this helps 
