pgmkernel



Pgmkernel User Manual(0)                              Pgmkernel User Manual(0)



Table Contents



NAME

       pgmkernel - generate a convolution kernel



SYNOPSIS

       pgmkernel

       [-weight w]

       width

       [height ]




DESCRIPTION

       This program is part of Netpbm(1).

       pgmkernel  generates a convolution kernel that you can use with pnmcon-
       vol.  The kernel is one where the weight of each location is  inversely
       proportional to its distance from the center of the kernel.

       pgmkernel  generates  a  PGM image of size width by height (or width by
       width if you don’t specify height).

       pgmkernel computes the convolution function K as follows.

       K(i,j) = 1 / ( 1 + w * sqrt(i^2 + j^2))

       where w is a coefficient specified via the -weight option.  i and j are
       measured  in  pixels.  K is zero everywhere beyond the specified kernel
       width and height.

       pgmkernel generates the output PGM file in the Plain  (text)  variation
       of PGM.



OPTIONS

       The  optional  -weight  value  should be a real number greater than -1.
       The default value is 6.0.



LIMITATIONS

       The computation time is proportional to width*height.   This  increases
       rapidly  with the increase of the kernel size.  A better approach could
       be using a FFT in these cases.



SEE ALSO

       pnmconvol(1), pnmsmooth(1) pamgauss(1) pgm(1)




AUTHOR

       Alberto Accomazzi (alberto@cfa.harvard.edu).



netpbm documentation           10 December 1992       Pgmkernel User Manual(0)

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