lapZeroCross
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Name
lapZeroCross - find zero crossing of lapacian
Syntax
#include <xite/convolve.h>
BiffStatus lapZeroCross( IBAND iband,
IBAND oband, int a, int b, int c,
double scale, double offset, int v );
Description
lapZeroCross finds the zero crossing of the laplacian
of the input band. The routine starts by calling the
laplace operator, followed by calling the crossing routine.
The output is zero where the laplacian has no zero
crossing, and proportional to the edge strength where
the laplacian has a zero crossing.
The arguments a, b, c, scale, offset and v are as
described for the laplace operator. Typical values are
a = 0, b = -1, c = 4, scale = 1.0, offset = 127.0.
The whole algorithm is:
<Calculate laplacian>;
FOR <every pixel (x,y)>:
IF <in(x,y) have zero crossing>
out(x,y) = MAX(ABS(in(x,y)-in(x+1,y)), \\
ABS(in(x,y)-in(x,y+1)))
ELSE
out(x,y) = 0
Restrictions
iband and oband must have pixel type unsigned byte.
See also
lapZeroCross(1), laplace(3), gradient(3), grad(3), roberts(3),
sobel(3), prewitt(3), contour(3), crossing(3)
Return value
0 => ok
1 => bad pixel type input band
2 => bad pixel type output band
3 => some error in crossing
Author
Tor Lønnestad, BLAB, Ifi, UiO
Id
$Id: lapZeroCross.c,v 1.23 1997/01/16 15:53:29 svein Exp $