# pgmkernel

Pgmkernel User **Manual(0)** Pgmkernel User **Manual(0)**
Table Contents

## NAME

pgmkernel - generate a convolution kernel

## SYNOPSIS

**pgmkernel**
[**-weight** *w*]
*width*
[*height* ]

## DESCRIPTION

This program is part of **Netpbm(1)**.
**pgmkernel** generates a convolution kernel that you can use with **pnmcon-**
**vol**. The kernel is one where the weight of each location is inversely
proportional to its distance from the center of the kernel.
**pgmkernel** generates a PGM image of size *width* by *height* (or *width* by
*width* if you donâ€™t specify *height*).
**pgmkernel** computes the convolution function K as follows.
K(i,j) = 1 / ( 1 + w * sqrt(i^2 + j^2))
where *w* is a coefficient specified via the **-weight** option. *i* and *j* are
measured in pixels. K is zero everywhere beyond the specified kernel
width and height.
**pgmkernel** generates the output PGM file in the Plain (text) variation
of PGM.

## OPTIONS

The optional **-weight** value should be a real number greater than -1.
The default value is 6.0.

## LIMITATIONS

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)** **pamgauss(1)** **pgm(1)**

## AUTHOR

Alberto Accomazzi (*alberto@cfa.harvard.edu*).
netpbm documentation 10 December 1992 Pgmkernel User **Manual(0)**

Man(1) output converted with
man2html