[mapserver-users] Corrupt image output

[Mike Leahy]

Tamas,

I just gave this a try a few times - deleted the cache, and loaded one 
tile.  It seems to happen less frequently, but I still have about a 1 in 
3 chance of getting various rectangle artifacts on the image.  It 
basically looks like something forgets to draw one or more of the rgb 
colours.

Mike

Tamas Szekeres wrote:
> Mike,
> 
> Did you experience the same problem when calling tile.php directly
> when rendering an individual tile?
> 
> Best regards,
> 
> Tamas
> 
> 
> 2008/8/19 Mike Leahy <mgleahy at alumni.uwaterloo.ca>:
>> Hello list,
>>
>> I'm wondering if anyone can help me figure out a problem I'm having with
>> corrupted output from from a tiled geotiff dataset I'm using in a ka-Map
>> environment.  You can see what's happening to the imagery here:
>> http://img527.imageshack.us/my.php?image=corrupthd1.png
>>
>> This generally happens when I'm zoomed in fairly close, and usually with
>> this high-resolution image dataset.  However, I can get corrupted output for
>> other raster datasets (all geotiff, but not always tiled).  It seems to
>> happen when the machine is processing most intensively (i.e., usually when
>> the imagery is being rendered by ka-Map).  It also seems to be limited to
>> the laptop I am using, which is running F7-x86_64.  In contrast, I have an
>> actual server (F8-x86_64), which has a virtually identical setup (with
>> respect to MapServer and its various dependencies), but with lots more cpu
>> cores and ram, and it's having no trouble at all (as far as I have noticed).
>>
>> The corruption in the output from the same application my laptop is not
>> always the same - if I clear the cache for ka-Map and re-render the images,
>> I'll get similar artifacts appearing in the output (red, green, blue and/or
>> black rectangles), but they will vary in size and location.  It happens for
>> both GD/AGG drivers, and JPEG/PNG output formats.
>>
>> Until now, I figured it was just a problem with limited memory on my laptop
>> (it was always around 100% when rendering this imagery on the web service +
>> viewing the application in a browser), but now I've upgraded the ram -
>> there's plenty of spare room and I'm still getting the same problem.  I just
>> finished upgrading Gdal from 1.5.0 to 1.5.2, and that didn't help any.
>>
>> Basically, the only real differences I can think of between my laptop and my
>> server are the number of cpu cores (1 on my laptop vs. 8 on the server), and
>> possibly the versions of some of the underlying libraries in the system.
>>  Does anyone know where I should start looking to find the cause of this?
>>  Or perhaps somebody recognizes this problem, and knows what I might be
>> doing wrong...
>>
>> Thanks for any suggestions,
>> Mike
>>
>> _______________________________________________
>> mapserver-users mailing list
>> mapserver-users at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/mapserver-users
>>
>