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pgmkernel

Langue: en

Version: 10 December 1992 (fedora - 01/12/10)

Section: 1 (Commandes utilisateur)

Table Contents

NAME

pgmkernel - generate a convolution kernel

SYNOPSIS

pgmkernel [-weight w] width [height ]

DESCRIPTION

This program is part of Netpbm(1).

pgmkernel generates a convolution kernel that you can use with pnmconvol. The kernel is one where the weight of each location is inversely proportional to its distance from the center of the kernel.

pgmkernel generates a PGM image of size width by height (or width by width if you don't specify height.

pgmkernel computes the convolution function K as follows.

K(i,j) = 1 / ( 1 + w * sqrt(i^2 + j^2))

where w is a coefficient specified via the -weight option. i and j are measured in pixels. K is zero everywhere beyond the specified kernel width and height.

pgmkernel generates the output PGM file in the Plain (text) variation of PGM.

OPTIONS

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

LIMITATIONS

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) pamgauss(1) pgm(1)

AUTHOR

Alberto Accomazzi (alberto@cfa.harvard.edu).

Une géométrie ne peut pas être plus vraie qu'une autre ; elle peut
seulement être plus commode.
-+- Henri Poincaré -+-