Converting between screen and geographical coordinates

[Francesco Antognini]

Sorry if this subject has been beaten to death, but I couldn't find a
precise answer in the archives.

As I went through the Mapserver  API I realized that no function to convert
from screen to geographical coordinates is available. This is not a big deal
for zooming as the methods take screen coordinates, but is for querying
layers.
The only hint I found is the click2map or Geo2Pix functions. However those
functions perform a linear transformation only, which may work fine in
limited areas but can be skewed in larger areas (or northern areas for
instance) depending on the projection used by the map.

So the question is whether a more precise method to convert screen
coordinates into geographical and back exists.

Thanks in advance for any help
Francesco
-- 
Francesco Antognini
Computer Consultant
Switzerland
fantognini at gmail.com
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