How to find real display density (DPI) from Java code?

Question

I\'m going to do some low-level rendering stuff, but I need to know real display DPI for making everything of correct size.

I\'ve found one way to do this: jav

Answer 1

Looks like it's currently possible to get it from java.awt.GraphicsEnvironment. Here's commented code example which does work on latest JDK (8u112).

// find the display device of interest
final GraphicsDevice defaultScreenDevice = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice();

// on OS X, it would be CGraphicsDevice
if (defaultScreenDevice instanceof CGraphicsDevice) {
    final CGraphicsDevice device = (CGraphicsDevice) defaultScreenDevice;

    // this is the missing correction factor, it's equal to 2 on HiDPI a.k.a. Retina displays
    final int scaleFactor = device.getScaleFactor();

    // now we can compute the real DPI of the screen
    final double realDPI = scaleFactor * (device.getXResolution() + device.getYResolution()) / 2;
}