How to make java use millimeters instead of pixels?

Question

My problem is that what I size a picture according to millimeters to pixels, and then print it out this will never be exact. My question is there a way to make java draw in millimeters or any other metric unit stead of pixels, because pixils will never be exact to millimeters.

Answer 1

Get the screen DPI using java.awt.Toolkit.getDefaultToolkit().getScreenResolution(); Then simply do (MM * DPI)/25.4 .
The outcome will be the amount of pixels relative to the physical length in MM.

Answer 2

If you know the resolution - px/cm you can do the calculation in centimeters I guess. However, printers and displays have different resolutions based on the hardware itself. In Photoshop for example you can define how many pixels per inch you desire. Whether a printer can actually print the defined density depends on the printer itself.

As an extreme example think about a 46 inch television and your smart phone. Both claim 1080 hd images but clearly the size in inches is drastically different.

Answer 3

Doing some analysis, you could understand better:

pixels = mm * inch/mm * pixels/inch
pixels = mm (milimeters) * 25.4 (how many inches I have in 1 mm) * DPI (screen resolution)

DPI is dots per inch, which is the same of pixels per inch.