Armin, GDAL's resampling algorithms for overviews are a bit restricted. Your best bet is to smoothen the image with an image processing software.
On Thu, Aug 5, 2010 at 11:00 PM, Armin Burger <[email protected]> wrote: > Chaitanya > > I send the image just to you since it's not small any more. This is a > mosaic of 3 versions of GDAL overviews: > > left: nearest > middle: cubic > right: gauss > > as you can see, nearest and cubic are looking very similar, quite grainy > (which I would expect from nearest but not from cubic convolution). The > gaussian on the other hand is very much smoothed, already a bit blurred. I > was expecting that cubic would produce much less grainy results than nearest > but less blurred effects than gaussian. > > Regards > Armin > > > On 05/08/2010 14:52, Chaitanya kumar CH wrote: > >> Armin, >> >> Can you provide a sample image that shows this problem? >> >> On Thu, Aug 5, 2010 at 5:57 PM, Armin Burger <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi all >> >> I have a question regarding the resampling modes for the gdaladdo >> utility. Since the overviews are used by Mapserver afterwards, I ran >> some tests with a map file referencing the Tiff image and the >> shp2img tool to output the results. >> >> I found the gauss resampling smoothening the image a bit too much. >> Therefore I wanted to try the "cubic" resample method using the GDAL >> version included in FWTools 2.4.7 (1.7.0b2), but to me it looks like >> that this does not have any effect compared to "nearest" resampling. >> Does anybody have a clue why? Command used was >> >> gdaladdo -ro -r cubic image.tif 2 4 8 16 32 64 >> >> Thanks in advance for any help >> Armin >> >> >> >> -- >> GMX DSL SOMMER-SPECIAL: Surf & Phone Flat 16.000 für nur 19,99 ¿/mtl.!* >> http://portal.gmx.net/de/go/dsl >> _______________________________________________ >> gdal-dev mailing list >> [email protected] <mailto:[email protected]> >> >> http://lists.osgeo.org/mailman/listinfo/gdal-dev >> >> >> >> >> -- Best regards, Chaitanya kumar CH. /tʃaɪθənjə/ /kʊmɑr/ +91-9494447584 17.2416N 80.1426E
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