Ken, KernelFilteredSource is derived from SimpleSource. It does not support setting a nodata value to the source band. Make sure your source image has a nodata value. You can set it using gdal_translate with the -a_nodata option.
On Fri, Nov 19, 2010 at 2:10 AM, Boss, Ken (DNR) <ken.b...@state.mn.us>wrote: > Chaitanya-- > > Thanks much for your response. > > I don't think that I described my problem effectively. Let me restate it > and see if we are talking about the same thing. > > Here is a .vrt file that I think should accomplish what I am after: > > <VRTDataset rasterYSize='690' rasterXSize='575'> > <SRS>EPSG:26915</SRS> > <GeoTransform>190000, 1000, 0, 4795000, 0, 1000</GeoTransform> > <VRTRasterBand band='1' dataType='Byte'> > <KernelFilteredSource> > > > <SourceFilename>D:/MyFiles/aptana_workspace/fire-webpage-mgmt/data/tmp_images/interpolated.tif</SourceFilename> > <SourceBand>1</SourceBand> > <NoDataValue>255</NoDataValue> > <Kernel normalized="1"> > <Size>5</Size> > <Coefs>0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 > 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04</Coefs> > </Kernel> > </KernelFilteredSource> > </VRTRasterBand> > </VRTDataset> > > I believe this file to be saying that interpolated.tif uses a value of 255 > for nodata, and that the kernel is to be normalized - that is, it should: > > o ignore any nodata pixels within the kernel window when operating on a > valid pixel > o adjust the coefficients to sum to one for the number of valid pixels in > the window when operating on a valid pixel > o do nothing at all when centered on a nodata pixel > > I would expect then that any pixels that go in as nodata should come out as > nodata, and that pixels with valid data values that are near nodata pixels > should not be influenced by them. > > However, the outputs are not what I expect. The averaging is applied to > both nodata and valid pixels alike. Have I set this up correctly, and is > there a bug somewhere, or (more likely) is my vrt improperly constructed? > > Thanks for your help, > > --Ken > > > -----Original Message----- > > From: Chaitanya kumar CH [mailto:chaitanya...@gmail.com] > > Sent: Wednesday, November 17, 2010 11:11 PM > > To: Boss, Ken (DNR) > > Cc: gdal-dev@lists.osgeo.org > > Subject: Re: [gdal-dev] KernelFilteredSource and nodata > > > > Ken, > > > > The current kernel filter does not ignore the boundaries of nodata > pixels. But it > > does normalize the kernel after ignoring the nodata pixels in the kernel, > if the > > 'normalized' attribute is set to 1. > > > > You can raise a ticket to request for this feature at > > http://trac.osgeo.org/gdal/newticket > > > >> On Thu, Nov 18, 2010 at 6:08 AM, Boss, Ken (DNR) <ken.b...@state.mn.us> > >> wrote: > >> Hello list-- > >> > >> I am attempting to filter a raster using gdal_translate (v 1.7) and a > vrt with a > >> KernelFilteredSource. The input raster contains large areas of "nodata" > values. I > >> would like the filter to ignore those areas. I have tried various > combinations of > >> <NoDataValue>, <HideNoDataValue>, <NODATA> and <Kernel normalized='1'>, > >> but have not been able to prevent the filter from applying itself at > data/nodata > >> boundaries. > >> > >> My current VRT and gdal_translate command lines are below. Can anyone > tell me > >> what I am doing wrong? > >> > >> Thanks, > >> > >> Ken Boss > >> Minnesota DNR > >> > >> ===== kernel_filter.vrt =================== > >> > >> <VRTDataset rasterYSize='690' rasterXSize='575'> > >> <SRS>EPSG:26915</SRS> > >> <GeoTransform>190000, 1000, 0, 4795000, 0, 1000</GeoTransform> > >> <VRTRasterBand band='1' dataType='Byte'> > >> <KernelFilteredSource> > >> <SourceFilename>interpolated.tif</SourceFilename> > >> <SourceBand>1</SourceBand> > >> <NoDataValue>255</NoDataValue> > >> <HideNoDataValue>1</HideNoDataValue> > >> <Kernel normalized='1'> > >> <Size>5</Size> > >> <Coefs>0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 > 0.04 0.04 0.04 > >> 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04 0.04</Coefs> > >> </Kernel> > >> </KernelFilteredSource> > >> </VRTRasterBand> > >> </VRTDataset> > >> > >> ===================================== > >> > >> gdal_translate -of GTiff -ot Byte -a_srs EPSG:26915 kernel_filter.vrt > >> kernel_filtered.tif > >> > > _______________________________________________ > > gdal-dev mailing list > > gdal-dev@lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/gdal-dev > > > > > > > > -- > > Best regards, > > Chaitanya kumar CH. > > /tʃaɪθənjə/ /kʊmɑr/ > > +91-9494447584 > > 17.2416N 80.1426E > -- Best regards, Chaitanya kumar CH. /tʃaɪθənjə/ /kʊmɑr/ +91-9494447584 17.2416N 80.1426E
_______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
