[gdal-dev] Return codes in gdalwarp

[Frank Warmerdam]

Michal Migurski wrote:
> Hello,
> 
> I think this is a bug report, or maybe a feature request.
> 
> I'm writing a script that shells out to gdalwarp. The GTiff files that I 
> might see as input to this script include palette and non-palette 
> images, and I'd like to be able to reliably compress the output without 
> human intervention.
> 
> Initially, I tried -co COMPRESS=JPEG on everything in the hopes that 
> gdalwarp would perform the necessary internal conversions to beat the 
> output into a JPEG. This didn't work with palette images, for which I 
> got an error like: "ERROR 1: JPEGSetupEncode:PhotometricInterpretation 3 
> not allowed for JPEG"
> 
> Then I tried setting up a loop that tries JPEG first followed by LZW, 
> but here I ran into difficulty recognizing a failure. The return code 
> for the palette images with all the errors is still 0, just like the 
> return code for a successful warp. The destination image is also 
> populated, so it's not possible to check for existence to determine 
> success.
> 
> What I'd love to see is a modification to the command-line behavior of 
> gdalwarp so it can be better used in a scripted setting, where automated 
> ways of detecting failure that don't require reading the error output 
> strings would be incredibly helpful. Ideally, choosing an incompatible 
> creation option would cause a non-zero exit and wouldn't create the 
> destination file.

Mike,

gdalwarp attempts to exit() with a non-zero result on failure in cases where
a problem is detected.  I imagine there are some failures to propagate some
kinds of errors back from the underlying layers - possibly even specific to
particular image drivers, or to the warp algorithm itself.

I would suggest filing a ticket with the particular case you encountered,
and enough information for us to easily reproduce the problem.

Best regards,
-- 
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