# 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).