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ppmspread(1) [minix man page]

ppmspread(1)                                                  General Commands Manual                                                 ppmspread(1)

ppmspread - displace a portable pixmap's pixels by a random amount SYNOPSIS
ppmspread amount [ppmfile] DESCRIPTION
Reads a portable pixmap as input. Moves every pixel around a bit relative to its original position. amount determines by how many pixels a pixel is to be moved around at most. Pictures processed with this filter will seem to be somewhat dissolved or unfocussed (although they appear more coarse than images pro- cessed by something like pnmconvol ). SEE ALSO
ppm(5), pnmconvol(1) AUTHOR
Copyright (C) 1993 by Frank Neumann 16 November 1993 ppmspread(1)

Check Out this Related Man Page

pnmconvol(1)                                                  General Commands Manual                                                 pnmconvol(1)

pnmconvol - general MxN convolution on a portable anymap SYNOPSIS
pnmconvol convolutionfile [pnmfile] DESCRIPTION
Reads two portable anymaps as input. Convolves the second using the first, and writes a portable anymap as output. Convolution means replacing each pixel with a weighted average of the nearby pixels. The weights and the area to average are determined by the convolution matrix. The unsigned numbers in the convolution file are offset by -maxval/2 to make signed numbers, and then normalized, so the actual values in the convolution file are only relative. Here is a sample convolution file; it does a simple average of the nine immediate neighbors, resulting in a smoothed image: P2 3 3 18 10 10 10 10 10 10 10 10 10 To see how this works, do the above-mentioned offset: 10 - 18/2 gives 1. The possible range of values is from 0 to 18, and after the off- set that's -9 to 9. The normalization step makes the range -1 to 1, and the values get scaled correspondingly so they become 1/9 - exactly what you want. The equivalent matrix for 5x5 smoothing would have maxval 50 and be filled with 26. The convolution file will usually be a graymap, so that the same convolution gets applied to each color component. However, if you want to use a pixmap and do a different convolution to different colors, you can certainly do that. At the edges of the convolved image, where the convolution matrix would extend over the edge of the image, pnmconvol just copies the input pixels directly to the output. SEE ALSO
pnmsmooth(1), pnm(5) AUTHORS
Copyright (C) 1989, 1991 by Jef Poskanzer. Modified 26 November 1994 by Mike Burns, 26 November 1994 pnmconvol(1)
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