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Pamgauss User Manual(0) Pamgauss User Manual(0)
NAME
pamgauss - create a two dimensional gaussian function as a PAM image
SYNOPSIS
pamgauss width height -sigma=number [-maxval=number] [-tuple-
type=string]
Minimum unique abbreviation of option is acceptable. You may use dou-
ble hyphens instead of single hyphen to denote options. You may use
white space in place of the equals sign to separate an option name from
its value.
EXAMPLES
pamgauss 3 3 -sigma=.5 -tupletype=GRAYSCALE | pamtopnm >gauss.pgm
pnmconvol -nooffset gauss.pgm myimage.ppm >blurred.ppm
DESCRIPTION
This program is part of Netpbm(1)
pamgauss generates a one-plane PAM image whose samples are a gaussian
function of their distance from the center of the image. I.e. the
sample value is highest in the center and goes down, in a bell curve
shape, as you move away from the center.
The values are scaled so that the volume under the surface of the two-
dimensional Gaussian function is the maxval of the image.
You can use this image as a convolution kernel with pnmconvol to blur
an image. (This technique is known as Gaussian blurring).
width and height are the dimensions of the image that pamgauss gener-
ates. Mathematically speaking, they are the domain of the two dimen-
sional gaussian function.
The sum of all the samples is equal to the image's maxval (within
rounding error). This is true even if you clip the Gaussian function
by making the image too small. If you want to be sure you get a whole
Gaussian function, make sure that you choose a sigma and image dimen-
sions so that if you made it any larger, the sample values at the edges
would be zero.
The output image is PAM. To make it usable with pnmconvol, specify
-tupletype=GRAYSCALE so pnmconvol can use it as if it were PGM. You
must use the -nooffset option on pnmconvol because zero means zero in
the PAM that pamgauss generates.
OPTIONS
-sigma=number
This is the sigma parameter of the Gaussian function (if it were
a Gaussian probability function, this would be its standard
deviation). The higher the number, the more spread out the
function is. Normally, you want to make this number low enough
that the function reaches zero value before the edge of your
image.
number is in units of pixels.
This option is required. There is no default.
-maxval=number
This is the maxval for the output image. It defaults to 255.
-tupletype=string
This is the value of the "tuple_type" attribute of the created
PAM image. It can be any string up to 255 characters. If you
don't specify this, pamgauss generates a PAM with unspecified
tuple type.
SEE ALSO
pnmconvol(1) , pamtopnm(1) , pgmkernel(1) , pamseq(1) , pam(5)
HISTORY
pamgauss was new in Netpbm 10.23 (July 2004).
netpbm documentation 8 May 2004 Pamgauss User Manual(0)
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