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)