pgmkernel (1)
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
AUTHOR
Alberto Accomazzi (alberto@cfa.harvard.edu).
| 
