[gdal-dev] Compression artifacts

[Jan Hartmann]

That would be an option. Am I right that the datasource of the -cutline 
option is a closed polygon, and that everything outside the polygon will 
be clipped?

However, I would prefer not to add extra steps. These are large maps and 
there are lots of them (about 17.000 for the whole of the Netherlands). 
It takes a lot of organisation to georeference them and display them 
efficiently over the web. Every additional processing step is a 
potential source of problems. So, although I am happy there is at least 
a workable solution, do you know what is happening here, and whether 
these artifacts can be prevented?

On 12/27/2012 01:44 PM, Dmitry Baryshnikov wrote:
> Hi Jan,
>
> You can cut result raster with the geometry (shape file) using 
> gdalwarp with cutline option (http://gdal.org/gdalwarp.html).
>
> Best regards,
>     Dmitry
>
> 27.12.2012 16:38, Jan Hartmann ?????:
>> Can anyone tell me wath is happening here? I have a large three-band 
>> raster (3.8G) looking like this:
>>
>> http://mapserver.sara.nl/map2a.png
>>
>> I compress it (from information from this list a few days ago) with:
>>
>> gdal_translate -co COMPRESS=JPEG -co PHOTOMETRIC=YCBCR big.tif small.tif
>> gdaladdo --config COMPRESS_OVERVIEW JPEG --config 
>> PHOTOMETRIC_OVERVIEW YCBCR -ro -r gauss small.tif 2 4 8 16 32 64
>>
>> and get a file of 37M, which is nice. However, the map has all kinds 
>> of rubbish at the borders. It looks like this:
>>
>> http://mapserver.sara.nl/map2b.png
>>
>> The equivalent pictures of a small part of the map look like this:
>>
>> http://mapserver.sara.nl/map1a.png
>> http://mapserver.sara.nl/map1b.png
>>
>> Can anyone help me?
>>
>> Jan
>>
>>
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>
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