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? 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 _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev
