Armin,<br><br>GDAL's resampling algorithms for overviews are a bit restricted. Your best bet is to smoothen the image with an image processing software.<br><br><div class="gmail_quote">On Thu, Aug 5, 2010 at 11:00 PM, Armin Burger <span dir="ltr"><<a href="mailto:armin.burger@gmx.net">armin.burger@gmx.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Chaitanya<br>
<br>
I send the image just to you since it's not small any more. This is a mosaic of 3 versions of GDAL overviews:<br>
<br>
left: nearest<br>
middle: cubic<br>
right: gauss<br>
<br>
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.<br>
<br>
Regards<br>
Armin<div class="im"><br>
<br>
On 05/08/2010 14:52, Chaitanya kumar CH wrote:<br>
</div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="im">
Armin,<br>
<br>
Can you provide a sample image that shows this problem?<br>
<br>
On Thu, Aug 5, 2010 at 5:57 PM, Armin Burger <<a href="mailto:armin.burger@gmx.net" target="_blank">armin.burger@gmx.net</a><br></div><div class="im">
<mailto:<a href="mailto:armin.burger@gmx.net" target="_blank">armin.burger@gmx.net</a>>> wrote:<br>
<br>
Hi all<br>
<br>
I have a question regarding the resampling modes for the gdaladdo<br>
utility. Since the overviews are used by Mapserver afterwards, I ran<br>
some tests with a map file referencing the Tiff image and the<br>
shp2img tool to output the results.<br>
<br>
I found the gauss resampling smoothening the image a bit too much.<br>
Therefore I wanted to try the "cubic" resample method using the GDAL<br>
version included in FWTools 2.4.7 (1.7.0b2), but to me it looks like<br>
that this does not have any effect compared to "nearest" resampling.<br>
Does anybody have a clue why? Command used was<br>
<br>
gdaladdo -ro -r cubic image.tif 2 4 8 16 32 64<br>
<br>
Thanks in advance for any help<br>
Armin<br>
<br>
<br>
<br>
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</div></blockquote></blockquote></div><br><br clear="all"><br>-- <br>Best regards,<br>Chaitanya kumar CH.<br>/tʃaɪθənjə/ /kʊmɑr/ <br>+91-9494447584<br>17.2416N 80.1426E<br>