[Chameleon] tiff hang

Paul Spencer pspencer at dmsolutions.ca
Tue Dec 7 20:31:20 EST 2004


this is very strange.  Chameleon is not aware of the image formats of 
the underlying data, it just uses mapscript to do the drawing.

Another solution to this problem may be to have the MapDHTML widget 
render the map to a file and then load the image source in the page 
rather than use drawmap.php.

We did this for another client who was having a strange problem with 
images half loading due to some sort of firewall problem (only in IE 

I've cc'd Assefa since he was the one who sorted that out.  Assefa, can 
you post the solution to getting MapDHTML to render to a file?  Do you 
think we could make this a configurable parameter in the MapDHTML widget 
(like DELAYDRAW="[true|false]" or something)?



Ken-ichi wrote:
> Thanks Paul.  I tried loading drawmap.php directly, and that usually 
> renders the map even when the Chameleon app hangs (though sometimes it 
> hangs too), so I guess drawmap.php may not actually be the culprit.  I 
> made another, minimal app with just the ZoomIn, ZoomOut, Recenter, and 
> MapDHTML widgets, and it still hangs on the tiffs, so I don't think it's 
> any of my custom widgets that are mucking things up either.
> I am really at a loss here.  The strangest thing about this is that if I 
> convert the TIFF to an Erdas Imagine file (either in Erdas or with 
> gdal_translate) everything works fine.  What is it about tiffs that 
> could possibly hang up Chameleon?  Why would Chameleon even be aware of 
> input file format?  Don't MapServer and GDAL handle that?  I know 
> they're fine because a non-Chameleon phpMapScript app renders the map 
> fine, as does the CGI.
> Argh.
> -Ken-ichi
> Paul Spencer wrote:
>> Ken,
>> to debug drawmap.php, you need to grab the URL from the image in the 
>> chameleon app and load it directly in your browser.  You should then 
>> see any error messages or debug output directly.  Often, problems with 
>> a broken map image are related to error messages (or notices) being 
>> output before the image contents, thus creating a corrupt image.
>> If nothing shows up immediately on viewing the drawmap.php url, you 
>> can then start to add some debugging code (echo) to drawmap.php to try 
>> to discover what is going on.
>> Cheers,
>> Paul
>> Ken-ichi wrote:
>>> Hi list.  A while ago I posted an issue I'd been having with 
>>> rendering TIFFs in Chameleon 
>>> (http://lists.maptools.org/pipermail/chameleon/2004-August/thread.html#1245), 
>>> but I never really resolved it.  Essentially, whenever I zoom in on a 
>>> GeoTIFF so that the TIFF fills the whole map, Chameleon hangs and 
>>> never displays the map image (I just get the spinner icon 
>>> indefinitely and then a broken image icon behind it.  Try zooming in 
>>> on the DRG (Test Raster) at
>>> http://fisher.cnr.berkeley.edu/vtm/data/mapbrowse/
>>> to see what I'm talking about.  I'm fairly sure this is a Chameleon 
>>> issue, most likely with drawmap.php, because this mapfile renders 
>>> just fine via the CGI, and with a rudimentary phpMapScript app like 
>>> this one:
>>> http://fisher.cnr.berkeley.edu/~kueda/mapscript_browse.phtml
>>> The DRG is a 16M GeoTIFF from the California Spatial Information 
>>> Library, so I don't think it's to blame.  You can check out my php 
>>> and MapScript config at
>>> http://fisher.cnr.berkeley.edu/~kueda/phpinfo_mapscript.phtml
>>> I'm running MapServer 4.4.0, GDAL 1.2.5, and PHP 4.3.9.  Can anyone 
>>> think of a reason this could be happening, or recommend a way to 
>>> troubleshoot drawmap.php?
>>> -Ken-ichi
>>> _______________________________________________
>>> Chameleon mailing list
>>> Chameleon at lists.maptools.org
>>> http://lists.maptools.org/mailman/listinfo/chameleon
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|Paul Spencer                           pspencer at dmsolutions.ca   |
|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|

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