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pgmedge.1
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1996-11-18
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.TH pgmedge 1 "04 February 1990"
.IX pgmedge
.SH NAME
pgmedge - edge-detect a portable graymap
.SH SYNOPSIS
.B pgmedge
.RI [ pgmfile ]
.SH DESCRIPTION
Reads a portable graymap as input.
Outlines the edges, and writes a portable graymap as output.
.IX "edge detection"
Piping the result through
.B pgmtopbm -threshold
and playing with the
threshold value will give a bitmap of the edges.
.IX thresholding
.PP
The edge detection technique used is to take the Pythagorean sum of
two Sobel gradient operators at 90 degrees to each other.
For more details see "Digital Image Processing" by Gonzalez and Wintz,
chapter 7.
.SH "SEE ALSO"
pgmenhance(1), pgmtopbm(1), pgm(5), pbm(5)
.SH AUTHOR
Copyright (C) 1991 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.