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pamgauss Updated: 8 May 2004 Table Of Contents NAME pamgauss - create a two dimensional gaussian function as a PAM image SYNOPSIS pamgauss -width -height -sigma=number [-maxval=number] [-tu- pletype=string] 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 3 3 -sigma=.5 -tupletype=GRAYSCALE | pamtopnm >gauss.pgm pnmconvol -nooffset gauss.pgm myimage.ppm >blurred.ppm DESCRIPTION This program is part of Netpbm. 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 area under the sur- face of the two-dimensional Gaussian function is the maxval of the image. You can use this image, converted to PGM, as a convolution kernel with pnmconvol to blur an image. (This technique is known as Gaus- sian blurring). width and height are the dimensions of the image that pamgauss generates. 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 Gaus- sian function, make sure that you choose a sigma and image dimensions so that if you made it any larger, the sample values at the edges would be zero. The output image is PAM. To turn it into a PGM that you can use with pnmconvol, specify -tupletype=GRAYSCALE and pass the output through pamtopnm. You must use the -nooffset option on pnmconvol be- cause zero means zero in the PAM that pamgauss generates. DESCRIPTION This program is part of Netpbm. -sigma=number This is the sigma parameter of the Gaussian function (if it were a Gaussian probability function, this would be its the 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 im- age. 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, pamtopnm, pgmkernel, pamseq, pam HISTORY pamgauss was new in Netpbm 10.23 (July 2004). _________________________________________________________________ Table Of Contents * NAME * SYNOPSIS * SYNOPSIS * DESCRIPTION * SEE ALSO * AUTHORS
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