Thanks a lot Jesse. I thought it could be like that but I wasn't sure. It's great you could spend time to answer such kind of questions. Best regards. Rodolphe
2009/4/7 Jesse Eichar <[email protected]> > > > On Tue, Apr 7, 2009 at 9:27 AM, Rodolphe QUEMERAIS < > [email protected]> wrote: > >> Thanks a lot. This works fine !!! >> >> But I didn't use any MathTransfrom. Actually, I picked 2 points : >> Coordinate world = getContext().pixelToWorld(e.x-1, e.y-1); >> Coordinate world2 = getContext().pixelToWorld(e.x+1, e.y+1); >> and created to envelope : >> Envelope env = new Envelope(world, world2); >> and the selection worked fine. >> > > >> My second question why do we have to do any operation with Mathtransform >> as >> getContext().pixelToWorld(...) do the transformation. >> Dis I miss something > > > > You need to understand the big picture. There are 3 frames of reference in > uDig: > > - THe Screen > - The Map > - The layer > > The Screen is always different from the map because the map takes place in > the world. Often -180:180,-90:90. So there is a pixelToWOrld transform > (and the opposite) to translate between the screen and the equivalent place > in the world. > > Next is the layer. The layer could be in the same projection as the map > but that is not a requirement. So if you set a selection on a layer the > selection must be in the projection of the layer. There is some work in the > pipeline to simplify that but that is the case at the moment. > > That is why you need a transformation from screen to map then from map to > layer. > > NO idea if I came close to answering your email but hopefully that helps in > some way > > Jesse > > _______________________________________________ > User-friendly Desktop Internet GIS (uDig) > http://udig.refractions.net > http://lists.refractions.net/mailman/listinfo/udig-devel > >
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