pgmkernel

   Updated: 10 December 1992
   Table Contents

NAME

   pgmkernel - generate a convolution kernel

SYNOPSIS

   pgmkernel [-weight w] width [height ]

DESCRIPTION

   This program is part of Netpbm.

   pgmkernel generates a convolution kernel that you can use with
pnmconvol.
   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	 flag.	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 flag should be a real number greater than
-1. The
   default value is 6.0.

LIMITATIONS

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

SEE ALSO

   pnmconvol, pnmsmooth pamgauss pgm

AUTHOR

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



Table Of Contents

     * NAME
     * SYNOPSIS
     * DESCRIPTION
     * OPTIONS
     * BUGS
     * SEE ALSO
     * AUTHOR

UNIX/Linux commands referenced on this page:

1. size
2. as
3. file
4. time
5. pnmconvol
6. pnmsmooth
7. pamgauss