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 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.
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).