Thx to read and think about my problem! :)
I have a map world image like that (mercator proj):
I have found this example (first of the page) which do this:
http://www.netzgesta.de/mapper/ (mouse lat/lon position is write at bottom/left map) but impossible to retrieve the function from the source..
So is there someone who got an idea? And I will need to do the opposite, pointer will be draggable and I will need to convet to lat/lon.
thanks Bertrand from france