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pgmkernel(1) [minix man page]

pgmkernel(1)                                                  General Commands Manual                                                 pgmkernel(1)

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 ( 10 December 1992 pgmkernel(1)

Check Out this Related Man Page

pbmtopgm(1)                                                   General Commands Manual                                                  pbmtopgm(1)

pbmtopgm - convert portable bitmap to portable graymap by averaging areas SYNOPSIS
pbmtopgm width height [pbmfile] DESCRIPTION
pbmtopgm reads a portable bitmap as input. It outputs a portable graymap in which each pixel's gray level is the average the surrounding black and white input pixels. The surrounding area is a rectangle of width by height pixels. In other words, this is a convolution. pbmtopgm is similar to a special case of pnmconvol. You may need a ppmsmooth step after pbmtopgm. pbmtopgm has the effect of anti-aliasing bitmaps which contain distinct line features. pbmtopgm works best with odd sample width and heights. You don't need pbmtopgm just to use a PGM program on a PBM image. Any PGM program (assuming it uses the Netpbm libraries to read the PGM input) takes PBM input as if it were PGM, with only the mininum and maximum gray levels. So unless your convolution rectangle is bigger than one pixel, you're not gaining anything with a pbmtopgm step. SEE ALSO
netpbm(1), pgmtopbm(1), pbm(5) AUTHOR
Copyright (C) 1990 by Angus Duggan Copyright (C) 1989 by Jef Poskanzer. Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, pro- vided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in sup- porting documentation. This software is provided "as is" without express or implied warranty. 03 Sep 2001 pbmtopgm(1)
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