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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
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.
Alberto Accomazzi (email@example.com).
10 December 1992 pgmkernel(1)
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