[mapserver-users] zoom out in phpmapscript: possible bug

[Assefa Yewondwossen]

I have added this in the bug list. I will look at it some times this week.

Thanks for the detailed explanations.

Claude Philipona wrote:

> Hello,
> I've observed a strange behaviour when we zoom out beyond the extent with
> php-mapscript. This problem appears only if the width/height ratio of the EXTENT
> is bigger than width/height ratio of the mapsize. Actually the map rendered is
> totally off the EXTENT limit. This totally reproducible. Let me explain the
> situation more in detail:
>
> PHP-Mapscript used:
> MapScript Version (Spet 13, 2001)
> MapServer version 3.5 (pre-alpha) OUTPUT=PNG OUTPUT=JPEG OUTPUT=WBMP
> SUPPORTS=PROJ SUPPORTS=TTF SUPPORTS=WMS INPUT=EPPL7 INPUT=JPEG INPUT=OGR
> INPUT=GDAL INPUT=SHAPEFILE
>
> EXTENT in .map file (unit meters)
> 490000 70000 840000 310000
> MAXSCALE 2000000
>
> which gives
> Width_EXTENT: 350000
> Height_EXTENT: 240000
>
> Ratio Width_EXTENT/Height_EXTENT= 1.4583
>
> ----> CASE 1: ratio_MAPSIZE > ratio_EXTENT (no bug, comportement is normal):
> we choose a map size:
> Width_MAPSIZE 600
> Height_MAPSIZE 400
>
> which gives a ratio of 1.5 so ratio_MAPSIZE > ratio_EXTENT
>
> We assume that the maxscale is set big enough so that when we zoom out, mapserver
> has to reajust to the EXTENT (in this example 2000000 is ok)
>
> Now we zoom out and we see that everything is normal. It comes a point when
> mapserver reajust automatically the BBOX to the EXTENT. The map is always
> properly placed inside the extent.
> returned BBOX: 490000 70000 840000 310000
>
> ----> CASE 2: ratio_MAPSIZE < ratio_EXTENT (buggy):
> we choose a map size:
> Width_MAPSIZE 600
> Height_MAPSIZE 500
>
> which gives a ratio of 1.2 so ratio_MAPSIZE < ratio_EXTENT
>
> We assume that the maxscale is set big enough so that when we zoom out, mapserver
> has to reajust to the EXTENT (in this example 2000000 is ok)
>
> Now we zoom out and we see that mapserver doesn't reajust properly when go beyond
> the EXTENT, mapserver doesn't reajust properly to the max EXTENT: Suddenly, there
> is a strong offset to the top, the map is almost totally off the extent limit. If
> we take a look at the returned BBOX, we see that mapserver has set y_max_extent
> to y_min_bbox, and a strange number to y_max_bbox:
> returned BBOX: 490000 310000 840000 361333.33333333
>
> This totally reproducible. I could also reproduce with gmap (with modification of
> mapsize). I'm almost  sure that it is bug, but not knowing the source code that
> well I couldn't find it. It seems to appear at least with zoompoint () and
> zoomscale().
>
> Has anyone an idea?
>
> Claude

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Assefa Yewondwossen
Software Analyst

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

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