PGMKERNEL

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).