On mercredi 4 octobre 2017 11:11:28 CEST Rahkonen Jukka (MML) wrote: > Hi, > > I was playing with kernel filters in VRT and using this really applies > sharpen filter on-the-fly when looking the image at native resolution with > QGIS: > > <VRTRasterBand dataType="Byte" band="1"> > <ColorInterp>Red</ColorInterp> > <KernelFilteredSource> > <SourceFilename relativeToVRT="1">image.tif</SourceFilename> > <SourceBand>1</SourceBand> > <SourceProperties RasterXSize="12000" RasterYSize="12000" > DataType="Byte" BlockXSize="12000" BlockYSize="1" /> <SrcRect xOff="0" > yOff="0" xSize="12000" ySize="12000" /> > <DstRect xOff="0" yOff="0" xSize="12000" ySize="12000" /> > <Kernel normalized="0"> > <Size>3</Size> > <Coefs>0 -1 0 -1 5 -1 0 -1 0</Coefs> > </Kernel> > </KernelFilteredSource> > </VRTRasterBand> > > However, filter is not applied to overviews which means that image looks > different when I zoom out. Is this the intended behavior?
I guess not from a user point of view. But looking at the code, I see: /* -------------------------------------------------------------------- */ /* For now we don't support filtered access to non-full */ /* resolution requests. Just collect the data directly without */ /* any operator. */ /* -------------------------------------------------------------------- */ if( nBufXSize != nXSize || nBufYSize != nYSize ) { return VRTComplexSource::RasterIO( nXOff, nYOff, nXSize, nYSize, pData, nBufXSize, nBufYSize, eBufType, nPixelSpace, nLineSpace, psExtraArg ); } (which means that over-sampling will also not apply the kernel) So seems the issue is "known". Probably that documenting this limitation should be done for now. Doc source is in frmts/vrt/vrt_tutorial.dox Even -- Spatialys - Geospatial professional services http://www.spatialys.com
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