[mapserver-users] problem with gdaladdo

[Holger Schiebold]

Hi everyvone,

I have a problem with gdaladdo while preprocessing raster images. For 
the output of raster images in a Mapserver application I use gdaladdo to 
build overviews of an image that represents Germany (gdaladdo -r 
average  test.tif 2 4 8 16 32 64 128 256 512 1024). Typically just the 
first 4 levels are used in the application. To get better output results 
from Mapserver I used the processing method "resample=average". But the 
problem for high quality output in the Mapserver application seems to be 
the great difference between the levels of the overviews. So I tried to 
build overviews with  gdaladdo -r average  test.tif  2 3 4 5 6 7 ....  
20. But now I have the problem that at the same zoomlevels in mapserver 
and in the pyramid (e.g. image at 500x500 pixel) the quality of the 
image is worse than in former case. Maybe gdaladdo does compute the next 
level not from the original image but from the previous level in the 
pyramid?  Is there a possibility to build the each overview from 
original image to get the best qualty in downsampled images?

thanks in advance

Holger Schiebold