Re: [Qgis-user] Building image pyramids - qgis crashing

[Maciej Sieczka]

Oleg Gusev pisze:
 Am Samstag 16 Februar 2008 00:57:28 schrieb Mikhail Umorin:
 ERROR 1: TIFFReadEncodedTile() failed.
 ...
 What is the problem and/or how can I track it down?

 It's a longstanding gdal bug for
 updating compressed .tiff tiles. The only
 known workaround is to disable compression.

A way to avoid such problems in future would be to modify QGIS not to 
build internal overviews (at least as an option). It could build 
external overviews instead, in .aux files.

The benefits of external overviews:

1. The input raster doesn't need to be uncompressed.
2. The input data are not modified.
3. Input data remain compatible with software that don't tolerate 
internal overviews.
4. Ergo - no need to duplicate data for safety/usability reasons before 
building overviews.
5. Other software support external overviews that GDAL creates - eg. 
ArcGIS, ERDAS Imagine.

What do developers think about it? Should I make an enhacement request?

Maciek

P.S.

For now, to create a external overwiev from CLI use eg.:
gdaladdo --config USE_RRD YES some.tif 2 4 8 16
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Re: [Qgis-user] Building image pyramids - qgis crashing

[Oleg Gusev]

Am Sonntag 17 Februar 2008 01:56:55 schrieb Mikhail Umorin:

 It's a longstanding gdal bug for
 updating compressed .tiff tiles. The only
 known workaround is to disable compression.

 How do I do that?

I'm usually using gdaladdo to create overviews, but
gdaladdo also has its own share of problems. The tile size is
hardcoded at 128x128 pixels, and sometimes it segfaults
on non-8bit paletted geotiffs. So this is more like a trial-and-error
solution.

 Oleg.

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