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