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.
Alberto Accomazzi (firstname.lastname@example.org).
10 December 1992 pgmkernel