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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