NAME
pamgauss - create a two-dimensional Gaussian function as a PAM imageSYNOPSIS
pamgauss width height -sigma=number [ -maxval= number] [ -tupletype=string] [ -maximize] [ -oversample=number] Minimum unique abbreviation of option is acceptable. You may use double 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 7 7 -sigma=.5 -maximize -tupletype=GRAYSCALE | pamtopnm >gauss.pgm pnmconvol -nooffset -normalize 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. You can use this image as a convolution kernel with pnmconvol to blur an image. (This technique is known as Gaussian blurring).OPTIONS
In addition to the options common to all programs based on libnetpbm (most notably -quiet, seeCommon Options ), pamgauss recognizes the following command line options:
- -sigma=number
- This is the standard deviation of the Gaussian function. 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 samples. This option is required. There is no default.
- -maximize
- Causes pamgauss to use the whole dynamic range available in the output PAM image by choosing an amplitude for the Gaussian function that causes the maximum value in the image to be the maxval of the image. If you select this, you probably want to normalize the output (scale the samples down so the volume under the surface of the two-dimensional Gaussian function is the maxval) before you use it, for example with pnmconvol's -normalize option. The reason this is different from just not using -maximize is that this subsequent normalization can be done with much more precision than can be represented in a PAM image. Without this option, pamgauss uses an amplitude that makes the volume under the surface of the two-dimensional Gaussian function the maxval of the image. This means all the samples in the image are normally considerably less than the maxval. This option was new in Netpbm 10.79 (June 2017).
- -maxval=number
- This is the maxval for the output image. 65535 is almost always the best value to use. But there may be some programs (not part of Netpbm) that can't handle a maxval greater than 255. The default is 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.
- -oversample=number
- This sets the oversampling factor. pamgauss samples the Gaussian function this many times, both horizontally and vertically, to get the value of each sample in the output. An oversampling factor of 1 means no oversampling, which means each sample is based only on the value of the Gaussian function at the center of the sample. The default is 5 divided by the standard deviation, rounded up to a whole number. This option was new in Netpbm 10.79 (June 2017). Before that, it is essentially 1 - there is no oversampling.
SEE ALSO
pnmconvol(1), pamtopnm(1), pgmkernel(1), pamseq(1), pam(1)HISTORY
pamgauss was new in Netpbm 10.23 (July 2004).DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML source. The master documentation is at18 May 2017 | netpbm documentation |