pgmedge(1)pgmedge(1)NAMEpgmedge - edge-detect a portable graymap
SYNOPSISpgmedge [pgmfile]
DESCRIPTION
Reads a portable graymap as input. Outlines the edges,
and writes a portable graymap as output. Piping the
result through pgmtopbm -threshold and playing with the
threshold value will give a bitmap of the edges.
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.
The maxval of the output is the same as the maxval of the
input The effect is better with larger maxvals, so you may
want to increase the maxval of the input by running it
through pnmdepth first.
SEE ALSOpgmenhance(1), pgmtopbm(1), pnmdepth(1), pgm(5), pbm(5)AUTHOR
Copyright (C) 1991 by Jef Poskanzer.
04 February 1990 pgmedge(1)