### 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 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.