getting xpinch and ypinch

Hello!

I would like to know if it is possible (and how) to get xpinch and ypinch 
values that R gets (from the system) for drawing plots.

If I understand correctly; with this values I could save the same picture as 
I see on computer 1 on computer 2 as a let say wmf file.

Thank you in advance,
Ales Ziberna