Re: [gdal-dev] gdaladdo and cubic resampling

[Chaitanya kumar CH]

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  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 > > 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
>>
>>
>>
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>>
>>
>>
>>


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Best regards,
Chaitanya kumar CH.
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[gdal-dev] gdaladdo and cubic resampling

[Armin Burger]

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


 
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