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pgmkernel
!!!pgmkernel
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
BUGS
SEE ALSO
AUTHOR
----
!!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((i-width/2)^2 +
(j-height/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).
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Last edited on Monday, June 3, 2002 6:50:54 pm by "perry"

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