[Mapserver-users] ECW not showing below certain scale

[Armin Burger]

Assefa, Frank

I tried too the new version of Mapserver with GDAL 1.2.1 and now I didn't encounter any more the errors I mentioned some days ago (that were similar to the ones Jacob found). Thanks again for the quick problem solving and providing of the new copiled version.

Armin

> I have put a new version of mapserver 4.3 (current CVS) build with GDAL
> 1.2.1 at
> http://www.maptools.org/php_mapscript/index.phtml?page=downloads.html
> (llok at the end of the page for the developpment verion). Let me know
> if it solves the ECW issue.

> Later,

> Frank Warmerdam wrote:

>> Delfos, Jacob wrote:
>>
>>> Hi All,
>>>
>>> I've been running into a little problem with mapserver 4.2, which I
>>> was also experiencing in Chameleon 1.99; when I zoom in quite far on
>>> the map (holding an ecw image), the map doesn't show up. It keeps
>>> trying to load, but nothing comes, suggesting it got stuck somewhere.
>>> CPU activity is initially at maximum for a few seconds (as normal when
>>> loading the map) but then drops while the map doesn't show (I'm
>>> loading the map in the browser on the server itself). The mapserv
>>> process won't allow itself to get killed either.
>>>
>>> If I simply replace my mapserv.exe file with one of version 4.0, the
>>> problem is gone. Of course the map takes quite a few seconds to show,
>>> which is normal when zooming close on an ECW, but it does show.
>>>
>>> I've tried this quite a few times in different browsers, but the map
>>> never shows at that scale when the ECW is in there. I have tried
>>> different mapfiles with different ECW's as well. Has the mechanism to
>>> display the ECW changed? It seems that as soon as I reach a resolution
>>> where I go beyond the ECW resolution (1pixel:1pixel) it dies.
>>
>>
>> Jacob,
>>
>> I was able to reproduce a problem with ECW supersampling when assertions
>> are turned on in GDAL 1.2.0.  I have just issued a GDAL 1.2.1 with this
>> issue
>> fixed, and suggested to Assefa that he upgrade to that as time permits.
>>
>> I am not absolutely positive if that is your problem or not.
>>
>> I suspect you are seeing differences between MapServer 4.0 and 4.2 because
>> MapServer 4.2 tries to use "dataset" level io calls when available.  This
>> allows reading red, green and blue in one pass against ECW for instance,
>> resulting in better performance.  However, it uses different code paths
>> which may have different issues.
>>
>> So ... if and when new binaries are available with GDAL 1.2.1 I would
>> suggest you try MapServer 4.2 again.  In the meantime you could just set an
>> appropriate MINSCALE so the ECW would stop rendering when supersampled,
>> or switch back to the build that works.
>>
>> Finally, I will once again strongly suggest that folks running into
>> problems
>> like this try and reproduce it at the commandline with shp2img and
>> appropriate
>> extent and debug options.  This often results in much more meaningful error
>> messages than you get on in a web application.
>>
>> Best regards,


> --
> ----------------------------------------------------------------
> 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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