Quoted from XDA August 15 2014 at 11:30 am by Will Verduzco:
"On mobile devices we never really had to deal with any analog issues... That’s because from the very outset mobile devices featured digital display technologies. That said there are still times in which it is good to be able to manually adjust certain display parameters. For example you may want to use a rather beefy case on your smartphone or tablet that happens to obscure part of the screen. Rather than simply not be able to see the missing screen real estate adjusting your display overscan settings would allow you to receive the missing data. Also if you ever wanted to connect your smartphone to your TV via HDMI you’ve surely noticed that many TVs apply their own under or overscan to the picture and either leave you with empty regions or missing content. Now with UI Tuner you can fix it.

UI Tuner works by letting you alter your phone’s default window settings. It allows you to change the density internally reported screen size overscan area and more. These settings can all be tweaked without the need to reboot."
You just click on Set Density/Screen Size/Overscan input your value in the given format and changes will take effect right away

UI Tuner also has some handy features like:
1. Keep Settings dialog (like on PC)
2. Auto start
3. Set on boot
4. Per app settings.

Contact me if you would like to translate this app in your language.

You can support the development of this app by buying the donation version.