How to get image coordinates in javascript?

Hi,

I am trying to do some code on getting mouse coordinates of an image in javascript, but the problem I am facing is that if image is say of size 2500 x 1000 but in browser its displayed as 1170 x 735 then I am able to get coordinates on 1170 x 735 only not the original size of 2500 x 1000.

How do I get coordinates of 2500x1000 ??? Please help.

Thanks.