Detecting DPI setting on client

[Guest]

I have set up an ImageButton on a webform. I am using it as a Image Map. I
use it's click event to return the coordinates to the server. But here is
the problem. The coordinates are affected by the screen's DPI setting. My
display is set to 120 DPI instead of the usual 96 DPI which is 125% more than
normal. To get the correct coordinate I need to divide the X and Y values by
1.25.

How can I get the correct coordinates regardless of the DPI setting on the
client. Is there a way to get the DPI setting from the client?

Any help would be greatly appreciated.
Thanks,
Rob