How to calculate the logical resolution of the phone?

The official mobile phone screen resolution ratio is the physical pixel ratio, such as ipone5 device resolution of 640*1136DP, the screen is 4 inches.

1. Calculate PPI

The PPI, or pixels per inch, represents the number of pixels (Pixel) owned per inch. Therefore, the higher the PPI value, which means that the display can display the image at higher density. Of course, the higher the density of the display, the higher the fidelity.

When your phone screen is 10-12 inches (about 25-30 centimeters) away from your eyes, its resolution is above the magic number of 300PPI (300 pixels per inch), and your retina is not able to tell the pixels, so the screen is called the retina screen. Because of its extremely high pixel density, the screen display is exceptionally clear and sharp. In general, the computer display screen has a resolution of 72PPI. If you want to know if your phone has a retina screen, you need to calculate the PPI on your phone's screen.

The PPI calculation formula is expressed as ppi=√ (x2+y2)/z (X: Length pixels, Y: width pixels; Z: Screen size). calculate formulas such as.

The PPI for iphone (1136^2+640^2)/4=326ppi, the screen belongs to the Retina screen, dpr=2, because 1px= (DPR) ^2*DP, so 1 logic pixels need two device pixels to render, that is, iphone5 of the logical pixel is 320*568.

How to calculate the logical resolution of the phone?