pgmedge (1)
edge-detect a portable graymap
SYNOPSIS
DESCRIPTION
Reads a portable graymap as input.
Outlines the edges, and writes a portable graymap as output.
"edge detection"
Piping the result through
pgmtopbm -threshold
and playing with the
threshold value will give a bitmap of the edges.
thresholding
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.
SEE ALSO
AUTHOR
Copyright (C) 1991 by Jef Poskanzer.
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