core/vil/algo/vil_trace_4con_boundary.cxx File Reference

Function to trace 4-connected boundary around region in bool image. More...

#include "vil_trace_4con_boundary.h"

Go to the source code of this file.

Functions
void	vil_next_4con_boundary_point (int &i, int &j, int &dir, const bool *&p, int ni1, int nj1, vcl_ptrdiff_t istep, vcl_ptrdiff_t jstep)
	Move (i,j) to next boundary point.
void	vil_trace_4con_boundary (vcl_vector< int > &bi, vcl_vector< int > &bj, const vil_image_view< bool > &image, int i0, int j0)
	Trace 4-connected boundary around region in boolean image.

---

Detailed Description

Function to trace 4-connected boundary around region in bool image.

Author:

Tim Cootes

Definition in file vil_trace_4con_boundary.cxx.

---

Function Documentation

void vil_next_4con_boundary_point	(	int &	i,
		int &	j,
		int &	dir,
		const bool *&	p,
		int	ni1,
		int	nj1,
		vcl_ptrdiff_t	istep,
		vcl_ptrdiff_t	jstep
	)		[inline]

Move (i,j) to next boundary point.

Start looking in direction dir (0=++x,1=++y,2=--x,3=--y) *p is current point (i,j). On exit (i,j) and p are updated to move to neighbour

Definition at line 12 of file vil_trace_4con_boundary.cxx.

void vil_trace_4con_boundary	(	vcl_vector< int > &	bi,
		vcl_vector< int > &	bj,
		const vil_image_view< bool > &	image,
		int	i0,
		int	j0
	)

Trace 4-connected boundary around region in boolean image.

Assumes that (i0,j0) is a boundary point. Searches for the boundary pixels and runs around until it gets back to beginning. On exit the boundary points are given by (bi[k],bj[k])

Assumes that (i0,j0) is a boundary point. Searches for the boundary pixels and runs around until it gets back to beginning. On exit the boundary points are given by (bi[k],bj[k])

Point to note: If (i0,j0) is in the middle of a 1 pixel wide line connecting two regions, then the point will occur twice in the list, once as the first point, then once in the middle of the list as we trace through it to get to the other side of the blob.

See also:

vil_trace_8con_boundary

Definition at line 52 of file vil_trace_4con_boundary.cxx.