PGMEDGE

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 operators at 90 degrees to each other.  For more
      details see "Digital Image Processing" by Gonzalez and Wintz, chapter
      7.

DEMONSTRATION

      Let a.pgm be a portable graymap.
      The following command will apply an edge filter on it:
        pgmmerge pgmedge a.pgm >aedge.pgm

BEFORE

AFTER

SEE ALSO

      pgmenhance(1), pgmtopbm(1), pgm(5), pbm(5)

AUTHOR

      Copyright (C) 1991 by Jef Poskanzer.