man > pgmkernel(1)

Che Dong

Generate a convolution kernel to be used with `pnmconvol`.

Generate a convolution kernel
pgmkernel {{width}} {{height}} > {{path/to/output.pgm}}
Generate a quadratic convolution kernel
pgmkernel {{size}} > {{path/to/output.pgm}}
Specify the weight of the center in the generated kernel
pgmkernel {{-w|-weight}} {{value}} {{width}} {{height}} > {{path/to/output.pgm}}

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  in‐
       crease 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 AT cfa.edu).




                                          10 December 1992                              pgmkernel(1)

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