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 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, pnmsmooth pamgauss pgm



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



netpbm documentation 10 December 1992 Pgmkernel User Manual(0)