home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
rtsi.com
/
2014.01.www.rtsi.com.tar
/
www.rtsi.com
/
OS9
/
OSK
/
NETWORK
/
netpbm_docs.lzh
/
NETPBM
/
DOCS
/
pgmkernel.1
< prev
next >
Wrap
Text File
|
1996-11-18
|
1KB
|
61 lines
.TH pgmkernel 1 "10 December 1992"
.IX pgmkernel
.SH NAME
pgmkernel - generate a convolution kernel
.SH SYNOPSIS
.B pgmkernel
[
.B \-weight
.I w
]
.I width
[
.I height
]
.SH DESCRIPTION
Generates a portable graymap array of size
.I width
x
.I height
(or
.I width
x
.I width
if
.I height
is not specified) to be used as a convolution file by
.BR pnmconvol .
The data in the convolution array K are computed according to the
formula:
.PP
K(i,j) = 1 / ( 1 + w * sqrt((i-width/2)^2 + (j-height/2)^2))
.PP
where
.I w
is a coefficient specified via the
.I \-weight
flag, and
.I width
and
.I height
are the X and Y filter sizes.
.PP
The output PGM file is always written out in ASCII format.
.SH OPTIONS
The optional
.I -weight
flag should be a real number greater than -1.
The default value is 6.0.
.SH BUGS
The computation time is proportional to
.I width
*
.IR height .
This increases rapidly with the increase of the kernel size.
A better approach could be using a FFT in these cases.
.SH "SEE ALSO"
pnmconvol(1), pnmsmooth(1)
.SH AUTHOR
Alberto Accomazzi (alberto@cfa.harvard.edu).