pgmkernel

 

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 pgmkernel(1)                                         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 con­
        volution 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)

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