[Gdal-dev] gdalwarp segfaults when -ot "COMPRESSION=..." used

[Frank Warmerdam]

On Sat, 29 Jan 2005 00:28:22 +0100, Maciek Sieczka <werchowyna at pf.pl> wrote:
> Hi All!
> 
> Long time no troubles with Gdal, happily - till today. I wanted to resample
> a 15 m, Float32, ArcInfoGrid DEM to 1 m. When no compression used it goes
> fine. But when -ot "COMPRESSION=..." is used a segfault occures (for either
> LZW, DEFLATE and PACKBITS). And I need the compression badly because the
> output is much too big. 

Maciek,

I have successfully reproduce the bug with a somewhat similar
configuration here.  I submitted a bug at:

  http://bugzilla.remotesensing.org/show_bug.cgi?id=757

I am guessing the problem is related to reading and rewriting
a compressed block in TIFF format.  When you have small output
files any given block will only be written once so things work.
When you have a large output file (especially one that is not
tiled), gdalwarp will handle the image in tiles and this can result
in scanlines getting written, re-read and then re-written with new
contents. 

In the past this was just unsupported for compressed files.  
However, Andrey has done some work in the last year or two
to allow rewriting compressed TIFF files.  But I would not be
surprised to find that in some circumstances this has some sort
of problem. 

Best regards,

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