redhat man page for pgmkernel

pgmkernel(1)						      General Commands Manual						      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.

SEE ALSO
       pnmconvol(1), pnmsmooth(1)

AUTHOR
       Alberto Accomazzi (alberto@cfa.harvard.edu).

								 10 December 1992						      pgmkernel(1)