Win8 and other devices after the DPI settings are too large to restore

Today's consumer electronics devices are getting smaller and smaller, but the resolution is increasing. For example, Surface Pro, 10.6-inch screen, 1080p full HD display will make the text displayed by Windows become abnormally small. This phenomenon is actually caused by the fact that the screen pitch is smaller than the standard (about 207.82 points /inch, and the standard is about 96 points /inch), although the display effect is more delicate, but Windows rendering of text is still the default DPI (it is 96 points/inch by the following), so the text becomes smaller.
To make the text look less difficult, our general approach is to enlarge the DPI of the system. In fact, this is a bit like the concept of PPI for digital image sampling. Assuming that Windows DPI is increased and the sampling resolution of Windows for UI elements is increased, the resampled UI elements will get a larger digital resolution than before. Both the length and the width get more pixels. On the same screen, it takes more display pixels than before, so the elements you see become larger.

Occasionally, in case we have customized an oversized DPI (for example, 500%), after applying and re-login, we can find that the system interface elements are too large, so we can no longer By manipulating the UI, go to the control panel and find this setting to change it back. At this point we have a correction method is to restart to safe mode.
The setting of DPI is user-dependent, that is, the DPI settings you make are only valid for your current user. Therefore, the DPI settings are also saved under the HKCU branch of the registry. A safer way to operate the registry directly is to reboot into safe mode, then change the DPI settings back to normal before restarting the computer. This is because the DPI zoom setting is not applied in safe mode and the size of all UI elements will return to normal.
Note that in the advanced startup options, if you select "Enable Low Resolution Video" mode, the size of the UI elements will be too large and will be exacerbated (because the resolution is lower). This mode can be used to solve some problems with the graphics driver, but the DPI settings are not related to the graphics driver, so please be careful to choose to enter safe mode to fix this problem.
If you still want to know where the DPI settings are stored in the registry, then for Win8, it is located under the HKEY_CURRENT_USERControl PanelDesktop project with the key name "LogPixels". By default, this key and key-value are not available in the system, but if you set DPI scaling, then this key appears. By default, the absolute value of DPI for Windows is actually 96, but it is not visible through the DPI settings interface. Here is the correspondence between DPI settings and registry keys:

It can be seen that the key value stored in the registry is the absolute value of the actual DPI, and the percentage displayed in the UI is based on "96 "= "100%" This definition. Therefore, after manually adjusting the DPI settings, you can easily calculate the true DPI value. For devices like Surface Pro, the system has automatically set the default DPI to 150%.