How do I fix a phone with a messed up dpi?

[AC Question]

My brother has a rooted LG G3 and he was using the app called Resolution Changer Pro and he messed up the dpi. The screen is now messed up. I asked him if he has USB debugging on and he says he most likely turned it off. I can't use the phone because the screen is useless. Is there a way I can use a computer or another device to change the dpi? USB connection as media device is turned off by the way.

 

[nahoku]

Can you start the phone in Safe Mode. Note the link is a generic Google search as you didn't specify your carrier. Pick the correct method. In Safe Mode, you might be able to undo what the app has done. Maybe even deleting the app data, or going as far as to uninstall the app.