[Mapserver-users] MapScript: map-Y coordinate is always wrong while map-X is right

[Lowell Filak]

By any chance does the Y result appear to be "mirrored" about the center
of the extent/map?
It may just be a matter of:
yMap = float(currentExtend[1])-cy*clickY
vs.
yMap = float(currentExtend[1])+cy*clickY
due to 0,0 on the image being top left and 0,0 in the extent being lower
left.
HTH
Lowell

The following message was sent by Bjoern Platzen <bplatzen at sosnetz.de>
on Tue, 8 Jul 2003 15:57:20 +0200.

> Hello List,
> 
> maybe I'm just to blind, but I can't figure out, what is going wrong.
> 
> I wrote a small Program using PythonMapscript. 
> 
> I'm calculating the following to get the Map-Coordinates from the 
> Click-Coordinates (where clickX and clickY come as img.x and img.y from 
> a HTML-form, Extend is the [mapext]):
> 
> def _click2map(self,clickX, clickY, Extend):
>     '''Uebersetze Klick-Koordinaten in Kartenkoordinaten'''
>     Extend = Extend.split(" ")
>     
>     cx = (float(Extend[2])-float(Extend[0]))/(self.mymap.width-1)
>     cy = (float(Extend[3])-float(Extend[1]))/(self.mymap.height-1)
>         
>     xMap = float(currentExtend[0])+cx*clickX
>     yMap = float(currentExtend[1])+cy*clickY
>     
>     return (xMap,yMap)
> 
> I took the function from a PerlMapScript Example. But it doesn't work 
> for me. The yMap is always wrong while the xMap is always right...
> 
> Maybe this comes because I have a mistake in my function that calculates 
> the Extend (mapext):
> 
> def _newExtend(self, Extend, zoomdir=0, zoomsize=1):
> 
>     currentExtend = Extend.split(" ")
>     
>     if zoomdir == 0:
>         zoom = 1
>     else:
>         zoom = zoomsize * zoomdir
>         if zoom < 0:
>             zoom = 1.0/abs(zoom)
>         
>     cx = self.mapXY[0]
>     cy = self.mapXY[1]
>         
>     he = float(currentExtend[2])-float(currentExtend[0])
>     wi = float(currentExtend[3])-float(currentExtend[1])
>     
>     self.mymap.extent.maxx = cx + (he/zoom)/2
>     self.mymap.extent.minx = cx - (he/zoom)/2
>     self.mymap.extent.maxy = cy + (wi/zoom)/2
>     self.mymap.extent.miny = cy - (wi/zoom)/2
>     return 1
> 
> The imgext is calculated this way:
> 
> def _imageExtend(self):
>     '''Finde den tatsaechlich sichtbaren Extent heraus'''
>     loleft = self._click2map(0,self.mymap.height,self.mapExtent)
>     upright = self._click2map(self.mymap.width,0,self.mapExtent)
>     Ext = str(loleft[0])+" "+str(loleft[1])+" "+str(upright[0])+" 
> "+str(upright[1])
>     return Ext
> 
> I hope, that there is anyone on the list, who can push me in the right 
> direction.
> 
> Thanks in advance,
> 
> Bjoern
> 
> -- 
> small office solutions
> info at sosnetz.de  -  http://www.sosnetz.de
> 
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