pgmkernel
Section: User Commands (1)
Updated: 10 December 1992
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NAME
pgmkernel  generate a convolution kernel
SYNOPSIS
pgmkernel
[
weight
w
]
width
[
height
]
DESCRIPTION
Generates a portable graymap array of size
width
x
height
(or
width
x
width
if
height
is not specified) to be used as a convolution file by
pnmconvol.
The data in the convolution array K are computed according to the
formula:
K(i,j) = 1 / ( 1 + w * sqrt((iwidth/2)^2 + (jheight/2)^2))
where
w
is a coefficient specified via the
weight
flag, and
width
and
height
are the X and Y filter sizes.
The output PGM file is always written out in ASCII format.
OPTIONS
The optional
weight
flag should be a real number greater than 1.
The default value is 6.0.
BUGS
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)
AUTHOR
Alberto Accomazzi (alberto@cfa.harvard.edu).
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 OPTIONS

 BUGS

 SEE ALSO

 AUTHOR

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