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pgmkernel - generate a convolution kernel

**pgmkernel**
[ **−weight** *w* ] *width* [
*height* ]

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.

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

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.

pnmconvol(1), pnmsmooth(1)

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

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