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 pnmconvol.  The kernel is one where the  weight
       of  each  location is inversely proportional to its dis-
       tance 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 fol-
       lows.

       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  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 199Pgmkernel User Manual(0)
