Decrease screen brightness below minimum level, by turning off individual pixels. This way the screen contrast is kept at the same level.
Save battery on newer AMOLED screens - they will turn off black pixels completely.
Tap app icon 3 times to show settings dialog.
Includes screen pattern editor.
Screen pattern is shifted each 5 minutes to prevent uneven pixel wear-out.
This app has limited functionality on Android 7 and newer, it cannot dim system buttons and notification area, because of new security model in Android 7.

App sources available here: https://github.com/pelya/screen-dimmer-pixel-filter