ppmconvol

Section: User Commands (1)
Updated: 14 April 1989
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NAME

ppmconvol - general MxN convolution on a portable pixmap  

SYNOPSIS

ppmconvol <convolutionfile> [ppmfile]  

DESCRIPTION

Reads two portable pixmaps as input. Convolves the second using the first, and writes a portable pixmap 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 immediate neighbors, resulting in a smoothed image:

    P1
    3 3
    1 1 1
    1 1 1
    1 1 1

The convolution file will usually be a bitmap or graymap instead of a pixmap, 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.  

SEE ALSO

ppm(5)  

AUTHOR

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, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. This software is provided "as is" without express or implied warranty.


 

Index

NAME
SYNOPSIS
DESCRIPTION
SEE ALSO
AUTHOR

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