nonsquare pixels
Brian Peschel
brianp at OCCINC.COM
Tue Feb 7 08:43:31 EST 2006
Frank,
I have added this into bugzilla as bug 1645 under the MapServer C
Library. This defaulted to be assigned to Stephen Lime (I couldn't see
who is assigned via the component until after I submitted it and I
didn't know what your user ID was in your bugzilla). I added a few
attachments to help show my problem.
I did upgrade to 4.8.1 yesterday and the problem persists (like you
expected).
I tried to debug a little (without much success) and it looks like the
call to msMapRestoreRealExtent() on line 627 of mapdraw.c might be
changing the extent? I am not using projection (I used an external
program to do my reprojection for this test) so I thought I might be
able to set map->gt.need_geotransform to false to prevent this.
However, since I don't know what map->gt.need_geotransform is really
doing, and I would like to add projection in the future, I didn't really
go much further than this.
Thanks for all you help here.....
- Brian
Frank Warmerdam wrote:
> On 2/3/06, Brian Peschel <brianp at occinc.com> wrote:
>
>> Well, I am not using the WMS dispatcher, so I see in msPrepareImage()
>> where the extents are changing for the 'fudge'. I do want non-square
>> pixels. So, I guessed that if I call:
>> msSetConfigOption(map, "MS_NONSQUARE", "YES");
>> before msDrawMap() I would get the exact extent I requested. However,
>> the extents are still changing, so I am missing another spot where the
>> extents are changing.
>>
>
> Brian,
>
> I think this should be sufficient.
>
>
>> My extent before calling msDrawMap is
>> EXTENT -113.981498074503 50.7247102624229 -113.961752952407
>> 50.7319757375771
>> my extent after the call is:
>> EXTENT -113.981498074503 50.7226042699327 -113.961752952407
>> 50.7340817300673
>>
>> whether I make the call to msSetConfigOoption() or not (I am using
>> msSaveMap() before and after the call to msDrawMap() to get the
>> extents). My image is 609x354 pixels (width x height).
>>
>> My resulting images are also blank (just the background color from my
>> map file).
>>
>> I am also running mapserver 4.6.2. I see that 4.8.0 is out. Would
>> upgrading help here?
>>
>
> I don't think you will fine much difference between 4.6.2 and
> 4.8.1 in this regard, but of course it is more interesting for
> the developers to debug if it is reproduced a recent version.
>
> Would it be possible for you to submit a demonstration of
> the problem via bugzillla? You can assign it directly to me
> since I am responsible for the messiness that is MS_NONSQUARE.
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush | Geospatial Programmer for Rent
>
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