Le lundi 18 avril 2016 22:35:42, Didier Bernard a écrit : > Hi Even, > > I can not use GDAL commands from command prompt. I have to resample my .tif > by using GDAL C# bindings. > > I manually created the previously shown .vrt file, based on examples from > GDAL .vrt tutorial page: http://www.gdal.org/gdal_vrttut.html > > I took one example from mentioned page, and replaced the > dataset.RasterXSize, dataset.RasterYSize and dataset.GetGeoTransform > values according to the data returned from the original (non-resampled: > "vesuvius_wgs84.tif") .tif file. > > What is wrong with the XML code of the .VRT file I posted in my previous > reply?
I'm not sure to understand what you do exactly... I'd recommand you do it manally with gdal_translate -of VRT to have a reference VRT, and then modify your code until it produces the same result. > > Thank you. > Didier > > ________________________________________ > From: Even Rouault <[email protected]> > Sent: Monday, April 18, 2016 10:25 PM > To: [email protected] > Cc: Didier Bernard > Subject: Re: [gdal-dev] Resampling a raster file with GDAL C# > > Le lundi 18 avril 2016 19:59:32, Didier Bernard a écrit : > > Hello, > > > > > > I am trying to resample a .tif raster in C# GDAL in a way that every > > other cell in a row and column is removed. > > > > Something similar to the lower GDAL command: > > gdal_translate -outsize 50% 0 input.tif output.tif > > > > But this command creates a new resampled .tif file. > > While I would like to avoid saving a new .tif file, and if possible just > > resample the dataset. > > > > It looks like this can be achieved by the use of VRT > > file<http://www.gdal.org/gdal_vrttut.html>. > > > > Here is one example of a .vrt file, which resamples the .tif file by > > removing the every other cell: > > > > > > <VRTDataset rasterXSize="42" rasterYSize="32"> > > > > <GeoTransform>14.3779166666, 0.000833333333333, 0.0, 40.8404166667, > > 0.0, > > > > -0.000833333333333</GeoTransform> <VRTRasterBand dataType="Byte" > > band="1"> > > > > <ColorInterp>Gray</ColorInterp> > > <SimpleSource resampling="bilinear"> > > > > <SourceFilename > > relativeToVRT="1">vesuvius_wgs84.tif</SourceFilename> > > <SourceBand>1</SourceBand> > > <SrcRect xOff="0" yOff="0" xSize="85" ySize="65"/> > > <DstRect xOff="0" yOff="0" xSize="42" ySize="32"/> > > > > </SimpleSource> > > > > </VRTRasterBand> > > > > </VRTDataset> > > It is not clear how you produced this VRT file. If you for example create > it with gdal_translate -of VRT, you'll see that the resolution is doubled. > > > What I noticed is that resolution of the resampled dataset does not > > change in comparison to the original dataset. > > > > In this case it remains the 0.00083 degrees. > > The same thing happens if I reproject the .tif file to some projected > > coordinate system (UTM for example): resolution remains the same (70 > > meters for example). > > > > Why is this the case? > > > > Shouldn't the resolution of the resampled dataset be twice of the > > resolution of the original (non-resampled) dataset, based on the fact > > that every other cell is removed (original dataset: 85x65, resampled > > dataset: 42x32)? > > > > > > I would be very grateful if I could get any kind of reply. > > > > Thank you in advance. > > > > With kind regards, > > Didier > > -- > Spatialys - Geospatial professional services > http://www.spatialys.com -- Spatialys - Geospatial professional services http://www.spatialys.com _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
