Google Static Map Problem

Question

I need to obtain static google map by passing latitude and longitude in the URL. this is Where i'm downloading the map image

google return the map image where the coordinates are of the center location of the map. i can download this image using the above URL.

PROBLEM: what i need is to get the X0 and Y0 coordinates of the image map.

are there any equation between pixel value and dgrees in real GPS coordinates??

Thank You