# pnmsmooth(1) [minix man page]

pnmsmooth(1) General Commands Manual pnmsmooth(1)NAME

pnmsmooth - smooth out an imageSYNOPSIS

pnmsmooth [width height] [-sizedumpfile] [pnmfile]-dumpDESCRIPTION

Smooths out an image by replacing each pixel with the average of its width X height neighbors. It is implemented as a C progam that gener- ates a PGM convolution matrix and then invokes pnmconvol.OPTIONS

width height Specifies the size of the convolution matrix. Default size is a 3x3 matrix. Width and height sizes must be odd. Maximum size of convolution matrix is limited by the maximum value for a pixel such that (width * height * 2) must not exceed the maximum pixel value.-sizedumpfile Generates and saves the convolution file only. Use of this option does not invoke pnmconvol.-dumpSEE ALSO

pnmconvol(1), pnm(5)AUTHORS

Copyright (C) 1989, 1991 by Jef Poskanzer. Converted from script to C program December 1994 by Mike Burns (burns@chem.psu.edu). 4 December 1994 pnmsmooth(1)

## Check Out this Related Man Page

pnmconvol(1) General Commands Manual pnmconvol(1)NAME

pnmconvol - general MxN convolution on a portable anymapSYNOPSIS

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'sto 9. The normalization step makes the range-9to 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.-1SEE ALSO

pnmsmooth(1), pnm(5)AUTHORS

Copyright (C) 1989, 1991 by Jef Poskanzer. Modified 26 November 1994 by Mike Burns, burns@chem.psu.edu 26 November 1994 pnmconvol(1)