[mapserver-users] PHP MapScript pixel coordinates to map coordinates

[Shorthouse, David]

Folks,

This question has no doubt been asked many times, but for the life of
me I cannot find a solution. Here's what I'm trying to do:

I have a jQuery-based front-end that uses the wonderful jcrop
extension (http://deepliquid.com/content/Jcrop.html) that helps
coordinate zoom. I'm hoping to use this same front-end to permit
cropping of a resultant map image, which means I need to pass the four
pixel corner coordinates, convert to map coordinates (projection may
be variable), then set the extent such that the resultant map image
will have the same dimensions as that described by the user on the
front-end. So, how can I convert pixel coordinates to map coordinates?
Note that the map projection is not always DD so I cannot merely use
proportions as I have seen in some solutions. Surely this is easier
than I am making it out to be.

Thanks for any advice,

David Shorthouse