[gdal-dev] gdalwarp fills nulls?

[William Kyngesburye]

Hmm, yes that one works for me.  I simplified my example for the  
email, maybe there's a memory problem, or raster size problem?

I originally tried to resample a GRASS raster DEM directly.  It's  
really 1000m cell size, 12809x18192 float cells, and want to resample  
to 21000m and 7000m.  That wasn't working so I exported to Geotiff  
(Int16 cells) with r.out.gdal.  The exported image has the nulls as  
-32768.  That doesn't work either.

... ah! memory!  I just tried with -wm 250 and I get the nulls.  And  
the nasty artifacts.  I think I want the nulls filled now ;)  I saw a  
bug about this on the tracker but it was fixed.  Maybe this is a  
different problem?

On Sep 10, 2009, at 5:56 PM, Even Rouault wrote:

> Selon William Kyngesburye <woklist at kyngchaos.com>:
>
> I don't manage to reproduce your issue neither with trunk nor with  
> 1.6.2 with a
> indem.tif generated by the following python script :
>
> import gdal
> import osr
>
> ds = gdal.GetDriverByName('GTiff').Create('indem.tif', 500, 500, 1,
> gdal.GDT_Int16)
> ds.SetGeoTransform([500000, 10, 0, 45000000, 0, -10])
> sr = osr.SpatialReference()
> sr.ImportFromEPSG(32631)
> ds.SetProjection(sr.ExportToWkt())
> ds.GetRasterBand(1).Fill(-32768)
> ds.GetRasterBand(1).SetNoDataValue(-32768)
> ones = ''
> for i in range(50*50):
>    ones = ones + '\001\000'
> ds.GetRasterBand(1).WriteRaster(225,225,50,50, ones, 25, 25)
> ds = None
>
>
> and
>
> gdalwarp -tr 100 100 -ot Int16 -r lanczos -dstnodata -32768  
> indem.tif outdem.tif
>
> You need to specify -dstnodata -32768. The result I get is as  
> expected a square
> of ones at the middle of nodata values at -32768 (except that due to  
> a strange
> behaviour of lanczos you get some artifacts at the edge of the  
> square).
>
>
>
>> Maybe I'm missing something?  I'm trying to resample a DEM, with  
>> null/
>> nodata values in oceans, using gdalwarp.  No matter what options I've
>> used so far, all the resampled nodata areas get filled with 0.
>>
>> GDAL 1.6.2
>>
>> So far I've tried (src res 10, nodata -32768 defined in src):
>>
>> gdalwarp -tr 100 100 -ot Int16 -r lanczos indem.tif outdem.tif
>> gdalwarp -tr 100 100 -ot Int16 -r lanczos -dstnodata -32768 indem.tif
>> outdem.tif
>> gdalwarp -tr 100 100 -ot Int16 -r lanczos -dstalpha indem.tif  
>> outdem.tif
>>
>> The last time I used gdalwarp, with nulls, was back at 1.5.x, and it
>> worked then, though I was projecting data (-t_srs), instead of only
>> resampling.  (I'd have to dig up an old 1.5 to see if it still works)
>>
>> -----
>> William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
>> http://www.kyngchaos.com/
>>
>> "I ache, therefore I am.  Or in my case - I am, therefore I ache."
>>
>> - Marvin
>>
>>
>> _______________________________________________
>> gdal-dev mailing list
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>>
>
>

-----
William Kyngesburye <kyngchaos*at*kyngchaos*dot*com>
http://www.kyngchaos.com/

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