[Gdal-dev] Gdalwarp - corrupt merge

[Frank Warmerdam]

Craig Miller wrote:
> When using gdalwarp on paletted geotiffs that have "TILED=YES" and
> "COMPRESS=LZW" set during creation I'm running into a couple of problems.  I
> confirmed via gdalinfo that all input files have the projection defined as
> EPSG:4326.
> 
> Problem #1
> Gdalwarp existing_file1.tif existing_file2.tif corrupts the second image.
> Projection is stripped, and none of my apps (non-gdal) can read the image
> (E.g. global mapper).  gdalinfo shows the projection being stripped, still
> paletted image.  Any suggestions on how to merge two geotiffs in this
> format?

Craig,

I don't see this result.  I suspect it relates to the specific version
of libtiff being used.  Some important fixes have gone into libtiff in
support of GDAL using it for random update to compressed files (ie.
gdalwarp using LZW compression).

You might want to try this with gdal's trunk (development) version,
and configured to use the internal libtiff (--with-tiff=internal).  If
the problem persists and we will see if we can reproduce it.

> Problem #2
> gdalwarp -te xmin ymin xmax ymax infile.tif outfile.tif
> Outputfile has no projection defined, compression is lost, and I assume
> tiling is too.
> Everything works ok if I specify -co options, -s_srs, -t_srs, etc but I
> thought it was supposed to output everything the same as the input.

I also do not see this result.  I just tried:

gdalwarp -te 440000 3720000 470000 3750000 utm.tif out.tif

and out.tif has the same coordinate system as the input file.  The compression
and tiling are not copied over.  These are considered to be file specific
options, and not part of the overall GDAL data model, so they do not carry
over to a copied file.

If you can file a bug demonstrating the coordinate system we can certainly
try and fix it, but this doesn't normally happen so it must be something
very specific to your situation.

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