pgmedge(1)                           General Commands Manual                           pgmedge(1)

NAME
       pgmedge - edge-detect a portable graymap

SYNOPSIS
       pgmedge [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 op‐
       erators 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 ALSO
       pgmenhance(1), pgmtopbm(1), pnmdepth(1), pgm(5), pbm(5)

AUTHOR
       Copyright (C) 1991 by Jef Poskanzer.

                                         04 February 1990                              pgmedge(1)

pgmedge: Use 'man pgmedge' for help.