How to calculate device pixel ratio

Question

I would like to know how the -webkit-device-pixel-ratio is calculated. I had already read this. Yet I am unable to understand it clearly. I would also like to know if there

Answer 1

claculate display metrics and get

DisplayMetrics dm = context.getResources().getDisplayMetrics(); int densityDpi = dm.densityDpi

and use dm.xdpi, or dm.ydpi i.e pixcel desity