[mapserver-users] Re: Corrupt image output
Mike Leahy
mgleahy at alumni.uwaterloo.ca
Tue Aug 19 04:04:28 PDT 2008
Hello again,
Just to follow-up on this, this problem isn't limited to just image
rendering. I also get odd results from raster queries in php mapscript
- about half the time, I'll get appropriate rgb values, but as you can
see in this example
(http://img411.imageshack.us/my.php?image=corrupt2rj9.png), I don't
always get the correct results. Often, I'll get zeros for all three
values, or just one value - in that sample image, the location on the
map indicated by the red dot should have something returned for all
three red/green/blue fields. So perhaps this is a problem somewhere
between mapscript and the gdal library?
Mike
Mike Leahy wrote:
> 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
>
>
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