Man page or keyword search:   man All Sections 1 - General Commands 2 - System Calls 3 - Subroutines, Functions 4 - Special Files 5 - File Formats 6 - Games and Screensavers 7 - Macros and Conventions 8 - Maintenence Commands 9 - Kernel Interface New Commands Server 4.4BSD AIX Alpinelinux Archlinux Aros BSDOS BSDi Bifrost CentOS Cygwin Darwin Debian DigitalUNIX DragonFly ElementaryOS Fedora FreeBSD Gentoo GhostBSD HP-UX Haiku Hurd IRIX Inferno JazzOS Kali Knoppix LinuxMint MacOSX Mageia Mandriva Manjaro Minix MirBSD NeXTSTEP NetBSD OPENSTEP OSF1 OpenBSD OpenDarwin OpenIndiana OpenMandriva OpenServer OpenSuSE OpenVMS Oracle PC-BSD Peanut Pidora Plan9 QNX Raspbian RedHat Scientific Slackware SmartOS Solaris SuSE SunOS Syllable Tru64 UNIXv7 Ubuntu Ultrix UnixWare Xenix YellowDog aLinux   6284 pages apropos Keyword Search (all sections) Output format html ascii pdf view pdf save postscript

pnmconvol(1)					 pnmconvol(1)

NAME
       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 rela-
       tive.

       Here is a sample convolution file; it does a simple  aver-
       age  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 offset that's -9 to 9. The  normaliza-
       tion  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.

SEE ALSO
       pnmsmooth(1), pnm(5)

AUTHOR
       Copyright (C) 1989, 1991 by Jef Poskanzer.

			 13 January 1991			1

                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 

Vote for polarhome