1Pgmkernel User Manual(0)                              Pgmkernel User Manual(0)
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5Table Contents ⟨#index⟩
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NAME

9       pgmkernel - generate a convolution kernel
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SYNOPSIS

13       pgmkernel [-weight w] width  [height ]
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DESCRIPTION

17       This program is part of Netpbm(1).
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19       pgmkernel  generates a convolution kernel that you can use with pnmcon‐
20       vol.  The kernel is one where the weight of each location is  inversely
21       proportional to its distance from the center of the kernel.
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23       pgmkernel  generates  a  PGM image of size width by height (or width by
24       width if you don't specify height.
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26       pgmkernel computes the convolution function K as follows.
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28       K(i,j) = 1 / ( 1 + w * sqrt(i^2 + j^2))
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30       where w is a coefficient specified via the -weight option.  i and j are
31       measured  in  pixels.  K is zero everywhere beyond the specified kernel
32       width and height.
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34       pgmkernel generates the output PGM file in the Plain  (text)  variation
35       of PGM.
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OPTIONS

39       The  optional  -weight  value  should be a real number greater than -1.
40       The default value is 6.0.
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LIMITATIONS

44       The computation time is proportional to width*height.   This  increases
45       rapidly  with the increase of the kernel size.  A better approach could
46       be using a FFT in these cases.
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SEE ALSO

50       pnmconvol(1), pnmsmooth(1) pamgauss(1) pgm(1)
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AUTHOR

55       Alberto Accomazzi (alberto@cfa.harvard.edu).
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59netpbm documentation           10 December 1992       Pgmkernel User Manual(0)