Raster zoom problem with ERDAS Imagine Files

[Frank Warmerdam]

On 7/13/05, Paul Moen <pmoen at state.nd.us> wrote:
> Greetings,
> 
> We seem to be having some problems with our color orthophotography. Our map service is using
> tiled county mosaics in an ERDAS Imagine (.img) (24 bit, RGB file) format. Errors will pop up in our
> 4.4 Mapserver instance when I try to zoom in past a scale of 1:9500 and color shifts occur after
> zooming past certain scales.
...
> The error is:
> 
> PHP Warning:  [MapServer Error]: IReadBlock failed at X offset 703, Y offset 675: GDALRasterIO()
> failed: drawGDAL() in drawmappm.php on line 105
> PHP Fatal error:  Call to a member function on a non-object in drawmappm.php on line 228

Paul, 

What platform are you working on?  GDAL 1.2.5 is a bit old now.  It
is possible an upgrade to GDAL 1.2.6 or GDAL CVS will help.  There
have been a few fixes in the decompression code in GDAL's Imagine
reader in the last year or two. 

Also, what platform are you on?  I am wondering if "large file" support
might not have been enabled at build time.   For instance, large files
were not supported on MacOS X with GDAL till quite recently (post 1.2.6).

This is clearly a GDAL problem, so you might just want to open a GDAL
bugzilla entry for the issue and we can pursue it from there.  

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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