[QGIS-trac] Re: [Quantum GIS] #605: Building pyramids causes segfault

[Quantum GIS]

#605: Building pyramids causes segfault
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        Reporter:  gsherman                                   |         Owner:  timlinux     
            Type:  defect                                     |        Status:  assigned     
        Priority:  critical: causes crash or data corruption  |     Milestone:  Version 1.0.0
       Component:  Rasters                                    |       Version:  0.8          
      Resolution:                                             |      Keywords:               
Platform_version:                                             |      Platform:  All          
        Must_fix:  Yes                                        |   Status_info:  0            
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Comment (by msieczka):

 Since my last #comment:4 regarding overwievs, I have learned that external
 overviews in *GeoTIFF* are also a nice option. They meet points 1-3 too,
 and although they are not so compatible as Erdas overviews, they are more
 compressable beacuse you can use DEFLATE for TIFF, which is more efficient
 than Erdas RLC compression method (the only available for Erdas, applied
 by default to Erdas overviews; and can't be disabled for overviews AFAIK).

 Compare (the input is a 361 MB uncompressed GeoTIFF):

 {{{
 $ gdaladdo --config USE_RRD YES atif.tif 2 4 8 16
 $ ls -sh atif.aux
 125M atif.aux
 }}}

 {{{
 $ chmod a-w atif.tif
 $ gdaladdo --config COMPRESS_OVERVIEW DEFLATE atif.tif 2 4 8 16
 $ ls -sh atif.tif.ovr
 103M atif.tif.ovr
 }}}

 So, ideally, QGIS should let the user choose if he wants internal
 overviews (and if/what compresssion scheme) or external overviews - in
 Erdas or GeoTIFF format (the former for better compatibility, the latter
 for space saving - if chosen let the user choose DEFLATE/LZW/PACKBITS;
 hint that DEFLATE compresses best and better than Erdas compressions).

-- 
Ticket URL: <https://trac.osgeo.org/qgis/ticket/605#comment:7>
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