Provided by: pktools_2.6.7.6+ds-2build2_amd64 bug

NAME

       pkfilter - program to filter raster images

SYNOPSIS

       pkfilter -i input -o output [-f filter | -srf file [-srf file]...  | -fwhm value [-fwhm value]...  ]
                [options] [advanced options]

DESCRIPTION

       pkfilter implements spatial and spectral filtering for raster data.  In the spatial domain  (X,  Y),  the
       filter typically involves a rectangular convolution kernel (moving window).  To avoid image shifting, the
       size of the window should be odd (3, 5, 7, ...).  You can set the window sizes  in  X  and  Y  directions
       separately with the options -dx and -dy.  A circular kernel (disc) is applied if option -circ is set.  An
       overview of the supported filters (option -f|--filter) is given below.  You can create customized filters
       by defining your own filter taps (multiplicative elements of the filter kernel) via an ascii file (option
       -tap).  In the spectral/temporal domain (Z) you can filter multi-band raster inputs.  The  kernel  filter
       size can be set with the option -dz (use odd values only).

   FILTERS IN SPATIAL (DX, DY) AND SPECTRAL/TEMPORAL (DZ) DOMAIN
       The number of output bands equals number of input bands

       Filter                Description
       dilate                morphological dilation
       erode                 morphological erosion
       close                 morpholigical closing (dilate+erode)
       open                  morpholigical opening (erode+dilate)
       smoothnodata values   smooth  nodata  values  (set --nodata
                             option!)

       Example: "Smooth" (interpolate) nodata in spectral/temporal domain (-dz 1), using a linear interpolation

       pkfilter -i input.tif -o smoothed.tif -dz 1 -f smoothnodata -interp linear

       Example: Filter input.tif in spatial domain with morphological dilation filter with kernel size 3x3.

       pkfilter -i input.tif -o dilated.tif -dx 3 -dy 3 -f dilate

       In case of moving window, the number of output bands equals number of input bands.   In  case  dz=1,  the
       single output band is calculated as the result of the statistical function applied to all bands.

       Filter       Description
       nvalid       report  number  of valid (not nodata)
                    values in window
       median       perform a median  filter  in  spatial
                    (dx,  dy)  or  spectral/temporal (dz)
                    domain
       var          calculate variance in window
       min          calculate minimum in window
       max          calculate maximum in window
       sum          calculate sum in window
       mean         calculate mean in window
       stdev        calculate   standard   deviation   in
                    window
       savgolay     Savitzky-Golay filter (check examples
                    page!)
       percentile   calculate percentile value in window
       proportion   calculate proportion in window

       Example: Median filter in spatial domain

       pkfilter -i input.tif -o median.tif -dx 3 -dy 3 -f median

       Example: Calculate statistical variance in spectral/temporal domain (single output band)

       pkfilter -i input.tif -o var.tif -dz 1 -f var

   WAVELET FILTERS
       The number of output bands equals number of input bands

       Filter    Description
       dwt       discrete wavelet transform
       dwti      discrete inverse wavelet transform
       dwt_cut   discrete wavelet + inverse transform,
                 using   threshold   option   to   cut
                 percentile of coefficients

       Example: Calculate discrete wavelet in spatial domain

       pkfilter -i lena.tif -o lena_dwt.tif -f dwt

       Example: Calculate discrete wavelet in spectral/temporal domain

       pkfilter -i timeseries.tif -o dwt.tif -f dwt -dz 1

       The number of output bands equals number of input bands

       Filter         Description
       dwt_cut_from   discrete wavelet + inverse transform,
                      setting     all     high    frequence
                      coefficients  to   zero   (scale   >=
                      threshold)

       Example:  Calculate  low  frequency  time  series  based  on  discrete  wavelet  +  inverse  transform in
       spectral/temporal domain, retaining only coefficients until scale 3.

       pkfilter -i timeseries.tif -o lowfrequency.tif -f dwt_cut_from -dz 1 -t 4

   FILTERS IN SPATIAL DOMAIN ONLY (DX, DY > 1 AND ODD).
       The number of output bands equals number of input bands.

       Filter                   Description
       mrf                      Markov random field
       ismin                    pixel is minimum?
       ismax                    pixel is maximum?
       shift                    perform  a  pixel  shift  in  spatial
                                window
       scramble                 scramble pixels in a spatial window
       mode (majority voting)   perform   a   majority   voring  (set
                                --class option)
       sobelx                   horizontal edge detection
       sobely                   vertical edge detection
       sobelxy                  diagonal edge detection (NE-SW)
       sobelyx                  diagonal edge detection (NW-SE)
       countid                  count digital numbers in window
       order                    rank pixels in order
       density                  calculated the density
       homog                    central pixel must  be  identical  to
                                all other pixels within window
       heterog                  central  pixel must be different than
                                all other pixels within window
       sauvola                  Sauvola's thresholding method

       Example: Sobel edge detection in horizontal direction

       pkfilter -i lena.tif -o sobelx.tif -f solbelx -dx 5 -dy 5

OPTIONS

       -i filename, --input filename
              input image

       -o filename, --output filename
              output classification image

       -f filter, --filter filter
              filter function (nvalid, median, var, min, max, sum,  mean,  dilate,  erode,  close,  open,  homog
              (central  pixel  must be identical to all other pixels within window), heterog (central pixel must
              be different than all other pixels within window),  sobelx  (horizontal  edge  detection),  sobely
              (vertical  edge  detection),  sobelxy  (diagonal  edge  detection  NE-SW),sobelyx  (diagonal  edge
              detection NW-SE), density, countid, mode (majority voting, only for classes), smoothnodata (smooth
              nodata  values  only)  values,  ismin, ismax, order (rank pixels in order), stdev, mrf, dwt, dwti,
              dwt_cut, dwt_cut_from, scramble, shift, savgolay, percentile, proportion)

       -dx value, --dx value
              filter kernel size in x, use odd values only

       -dy value, --dy value
              filter kernel size in y, use odd values only

       -dz value, --dz value
              filter kernel size in z (band or spectral dimension), must be odd (example: 3).  Set dz>0  if  1-D
              filter must be used in band domain

       -nodata value, --nodata value
              nodata value(s) (used for smoothnodata filter)

       -v level, --verbose level
              verbose mode if > 0

       Advanced options

       -circ, --circular
              circular disc kernel for dilation and erosion

       -r method, --resampling-method method
              Resampling   method   for   shifting  operation  (near:  nearest  neighbour,  bilinear:  bi-linear
              interpolation).

       -co option, --co option
              Creation option for output file.  Multiple options can be specified.

       -wt type, --wavelet type
              wavelet type: daubechies,daubechies_centered, haar, haar_centered, bspline, bspline_centered

       -wf family, --wf family
              wavelet family (vanishing moment, see  also  http://www.gnu.org/software/gsl/manual/html_node/DWT-
              Initialization.html)

       -class value, --class value
              class value(s) to use for density, erosion, dilation, openening and closing, thresholding

       -t threshold, --threshold threshold
              threshold  value(s)  to  use  for  threshold  filter (one for each class), or threshold to cut for
              dwt_cut (use 0 to keep all) or dwt_cut_from, or sigma for shift

       -tap filename, --tap filename
              text file containing taps used for spatial filtering (from ul  to  lr).   Use  dimX  and  dimY  to
              specify tap dimensions in x and y.  Leave empty for not using taps

       -tapz value, --tapz value
              taps used for spectral filtering

       -pad method, --pad method
              Padding  method for filtering (how to handle edge effects).  Choose between: symmetric, replicate,
              circular, constant (pad with 0).

       -fwhm value, --fwhm value
              list of full width half to apply spectral filtering (-fwhm band1 -fwhm band2 ...)

       -srf filename, --srf filename
              list of ASCII files containing spectral response functions (two columns: wavelength response)

       -win col, --wavelengthIn col
              column number of input ASCII file containing wavelengths

       -wout value, --wavelengthOut value
              list of wavelengths in output spectrum (-wout band1 -wout band2 ...)

       -down value, --down value
              down sampling factor.  Use  value  1  for  no  downsampling).   Use  value  n>1  for  downsampling
              (aggregation)

       -beta filename, --beta filename
              ASCII file with beta for each class transition in Markov Random Field

       -eps value, --eps value
              error marging for linear feature

       -l1, --l1
              obtain longest object length for linear feature

       -a1, --a1
              obtain angle found for longest object length for linear feature

       -a2, --a2
              obtain angle found for shortest object length for linear feature

       -interp type, --interp type
              type          of         interpolation         for         spectral         filtering         (see
              http://www.gnu.org/software/gsl/manual/html_node/Interpolation-Types.html)

       -ot type, --otype type
              Data type for output image ({Byte / Int16 / UInt16 / UInt32 / Int32 / Float32 / Float64 / CInt16 /
              CInt32 / CFloat32 / CFloat64}).  Empty string: inherit type from input image

       -of GDALformat, --oformat GDALformat
              Output image format (see also gdal_translate(1)).

       -ct filename, --ct filename
              color  table  (file with 5 columns: id R G B ALFA (0: transparent, 255: solid)).  Use none to omit
              color table

EXAMPLE

       Filtering in spatial domain

       Filter input.tif with morphological dilation filter.  Use a circular kernel (instead of  rectangular)  of
       size 3x3.

       pkfilter -i input.tif -o filter.tif -dx 3 -dy 3 -f dilate -circ

       Similar  to  previous  example,  but consider only values of 255 for filtering operation.  Typical usage:
       dilate cloud values in input image that are flagged as 255

       pkfilter -i input.tif -o filter.tif -dx 3 -dy 3 -class 255 -f dilate -circ

       Filtering in spectral/temporal domain

       Calculate the median value for each pixel, calculated on a moving window of width  3  (-dz  3)  over  all
       input bands.  The output raster dataset will contain as many bands as the input raster dataset.

       pkfilter -i input.tif -o filter_stdev.tif -dz 3 -f median

       No  moving  window  (-dz  1).   Calculate  the standard deviation for each pixel, calculated on all input
       bands.  The output raster dataset will contain a single band only.

       pkfilter -i input.tif -o filter_stdev.tif -dz 1 -f stdev

       "Smooth" (interpolate) nodata in spectral/temporal domain (-dz 1), using  a  linear  interpolation.   The
       following   interpolation   types   are   supported:   akima   (default),  linear,  polynomial,  cspline,
       cspline_periodic, akima_periodic (please check gsl ⟨http://www.gnu.org/software/gsl/manual/html_node/
       Interpolation-Types.html⟩ page for more information on the interpolation types).

       pkfilter -i input.tif -o input_smoothed.tif -dz 1 -f smoothnodata -interp linear

                                                10 February 2020                                     pkfilter(1)