nonsquare pixels

[Brian Peschel]

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
>