[gdal-dev] KernelFilteredSource and nodata

[Boss, Ken (DNR)]

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