[mapserver-users] I have a question about the GMapPix2Geo function (listedbelow).

[Yewondwossen Assefa]

Do you have any values for which the function fails ?

PS : this function has been used in the GMap demo for some time now. I do not think that there is a problem with it but ...

Later

Debbie Pagurek wrote:

> I have a question about the GMapPix2Geo function (listed below).
> I have a map of the world showing in lat long.  The below function only seems to work if I am zoomed IN really far and it doesn't work if I am at the full extent of the map (minx=-180, maxx=180, miny=-90, maxy=90)
>
> Can anyone comment on this?  I wanted to build a mouseover function that will show the coordinates of the mouse position in the windows status bar.
>
> Thanks,
> D. Pagurek
>
> /************************************************************************/
> /*function GMapPix2Geo($nPixPos, $dfPixMin, $dfPixMax, $dfGeoMin,dfGeoMax, $nInversePix)                              */
> /*      Utility function to convert a pixel position to geocoded            position.                                                       */
> /*                                                                      */
> /*       The parameter $nInversePix could be set to 1 for Y pixel coordinates where the UL > LR. Else set to 0.                   */
> /************************************************************************/
> function GMapPix2Geo($nPixPos, $dfPixMin, $dfPixMax, $dfGeoMin, $dfGeoMax, $nInversePix)
> {
>    // $nPixPos : pixel position (X or Y)
>    // $dfPixMin, $dfPixMax : Pixel minimum and maximum (X or Y) of your map on the screen (should be 0 to xxx)
>   //  $dfGeoMin, $dfGeoMax : Geographic coordinate min max (X or Y) of your map on the screen
>
>     $dfWidthGeo = $dfGeoMax - $dfGeoMin;
>     $dfWidthPix = $dfPixMax - $dfPixMin;
>
>
>     $dfPixToGeo = $dfWidthGeo / $dfWidthPix;
>
>     if (!$nInversePix)
>         $dfDeltaPix = $nPixPos - $dfPixMin;
>     else
>         $dfDeltaPix = $dfPixMax - $nPixPos;
>
>     $dfDeltaGeo = $dfDeltaPix * $dfPixToGeo;
>
>     $dfPosGeo = $dfGeoMin + $dfDeltaGeo;
>
>     return ($dfPosGeo);
> }

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Assefa Yewondwossen
Software Analyst

Email: assefa at dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056 (ext 14)
Fax:   (613) 565-0925
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