pgmkernel(1) pgmkernel(1)
**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 con-
volution 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).
10 December 1992 1