vtkLinkEdgels Class Reference

#include <vtkLinkEdgels.h>

Inheritance diagram for vtkLinkEdgels:

[legend]Collaboration diagram for vtkLinkEdgels:

[legend]List of all members.

Detailed Description

links edgels together to form digital curves.

vtkLinkEdgels links edgels into digital curves which are then stored as polylines. The algorithm works one pixel at a time only looking at its immediate neighbors. There is a GradientThreshold that can be set that eliminates any pixels with a smaller gradient value. This can be used as the lower threshold of a two value edgel thresholding.

For the remaining edgels, links are first tried for the four connected neighbors. A successful neighbor will satisfy three tests. First both edgels must be above the gradient threshold. Second, the difference between the orientation between the two edgels (Alpha) and each edgels orientation (Phi) must be less than LinkThreshold. Third, the difference between the two edgels Phi values must be less than PhiThreshold. The most successful link is selected. The measure is simply the sum of the three angle differences (actually stored as the sum of the cosines). If none of the four connect neighbors succeeds, then the eight connect neighbors are examined using the same method.

This filter requires gradient information so you will need to use a vtkImageGradient at some point prior to this filter. Typically a vtkNonMaximumSuppression filter is also used. vtkThresholdEdgels can be used to complete the two value edgel thresholding as used in a Canny edge detector. The vtkSubpixelPositionEdgels filter can also be used after this filter to adjust the edgel locations.

See also:: vtkImageData vtkImageGradient vtkImageNonMaximumSuppression

Created by:

Martin, Ken

CVS contributions (if > 5%):

Martin, Ken (77%)
Law, Charles (8%)

CVS logs (CVSweb):

.cxx (/Graphics/vtkLinkEdgels.cxx)
.h (/Graphics/vtkLinkEdgels.h)

Tests:: vtkLinkEdgels (Tests)

Definition at line 71 of file vtkLinkEdgels.h.

Public Types

typedef vtkStructuredPointsToPolyDataFilter Superclass

Public Member Functions

virtual const char * GetClassName ()

virtual int IsA (const char *type)

void PrintSelf (ostream &os, vtkIndent indent)

virtual void SetLinkThreshold (double)

virtual double GetLinkThreshold ()

virtual void SetPhiThreshold (double)

virtual double GetPhiThreshold ()

virtual void SetGradientThreshold (double)

virtual double GetGradientThreshold ()

Static Public Member Functions

int IsTypeOf (const char *type)

vtkLinkEdgels * SafeDownCast (vtkObject *o)

vtkLinkEdgels * New ()

Protected Member Functions

vtkLinkEdgels ()

~vtkLinkEdgels ()

void Execute ()

void LinkEdgels (int xdim, int ydim, double *image, vtkDataArray *inVectors, vtkCellArray *newLines, vtkPoints *newPts, vtkDoubleArray *outScalars, vtkDoubleArray *outVectors, int z)

Protected Attributes

double GradientThreshold

double PhiThreshold

double LinkThreshold

Member Typedef Documentation

typedef vtkStructuredPointsToPolyDataFilter vtkLinkEdgels::Superclass

Reimplemented from vtkStructuredPointsToPolyDataFilter.
Definition at line 74 of file vtkLinkEdgels.h.

Constructor & Destructor Documentation

vtkLinkEdgels::vtkLinkEdgels ( ) [protected]

vtkLinkEdgels::~vtkLinkEdgels ( ) [inline, protected]

Definition at line 102 of file vtkLinkEdgels.h.

Member Function Documentation

virtual const char* vtkLinkEdgels::GetClassName ( ) [virtual]

Reimplemented from vtkStructuredPointsToPolyDataFilter.

int vtkLinkEdgels::IsTypeOf ( const char * type ) [static]

Return 1 if this class type is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.
Reimplemented from vtkStructuredPointsToPolyDataFilter.

virtual int vtkLinkEdgels::IsA ( const char * type ) [virtual]

Return 1 if this class is the same type of (or a subclass of) the named class. Returns 0 otherwise. This method works in combination with vtkTypeRevisionMacro found in vtkSetGet.h.
Reimplemented from vtkStructuredPointsToPolyDataFilter.

vtkLinkEdgels* vtkLinkEdgels::SafeDownCast ( vtkObject * o ) [static]

Reimplemented from vtkStructuredPointsToPolyDataFilter.

void vtkLinkEdgels::PrintSelf ( ostream & os,

vtkIndent indent

) [virtual]

Methods invoked by print to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.
Reimplemented from vtkStructuredPointsToPolyDataFilter.

vtkLinkEdgels* vtkLinkEdgels::New ( ) [static]

Construct instance of vtkLinkEdgels with GradientThreshold set to 0.1, PhiThreshold set to 90 degrees and LinkThreshold set to 90 degrees.
Reimplemented from vtkAlgorithm.

virtual void vtkLinkEdgels::SetLinkThreshold ( double ) [virtual]

Set/Get the threshold for Phi vs. Alpha link thresholding.

virtual double vtkLinkEdgels::GetLinkThreshold ( ) [virtual]

Set/Get the threshold for Phi vs. Alpha link thresholding.

virtual void vtkLinkEdgels::SetPhiThreshold ( double ) [virtual]

Set/get the threshold for Phi vs. Phi link thresholding.

virtual double vtkLinkEdgels::GetPhiThreshold ( ) [virtual]

Set/get the threshold for Phi vs. Phi link thresholding.

virtual void vtkLinkEdgels::SetGradientThreshold ( double ) [virtual]

Set/Get the threshold for image gradient thresholding.

virtual double vtkLinkEdgels::GetGradientThreshold ( ) [virtual]

Set/Get the threshold for image gradient thresholding.

void vtkLinkEdgels::Execute ( ) [protected, virtual]

This method is the old style execute method
Reimplemented from vtkSource.

void vtkLinkEdgels::LinkEdgels ( int xdim,

int ydim,

double * image,

vtkDataArray * inVectors,

vtkCellArray * newLines,

vtkPoints * newPts,

vtkDoubleArray * outScalars,

vtkDoubleArray * outVectors,

int z

) [protected]

Member Data Documentation

double vtkLinkEdgels::GradientThreshold [protected]

Definition at line 109 of file vtkLinkEdgels.h.

double vtkLinkEdgels::PhiThreshold [protected]

Definition at line 110 of file vtkLinkEdgels.h.

double vtkLinkEdgels::LinkThreshold [protected]

Definition at line 111 of file vtkLinkEdgels.h.

The documentation for this class was generated from the following file:

dox/Graphics/vtkLinkEdgels.h


Public Types
typedef vtkStructuredPointsToPolyDataFilter	Superclass
Public Member Functions
virtual const char *	GetClassName ()
virtual int	IsA (const char *type)
void	PrintSelf (ostream &os, vtkIndent indent)

virtual void	SetLinkThreshold (double)
virtual double	GetLinkThreshold ()

virtual void	SetPhiThreshold (double)
virtual double	GetPhiThreshold ()

virtual void	SetGradientThreshold (double)
virtual double	GetGradientThreshold ()
Static Public Member Functions
int	IsTypeOf (const char *type)
vtkLinkEdgels *	SafeDownCast (vtkObject *o)
vtkLinkEdgels *	New ()
Protected Member Functions
	vtkLinkEdgels ()
	~vtkLinkEdgels ()
void	Execute ()
void	LinkEdgels (int xdim, int ydim, double image, vtkDataArray inVectors, vtkCellArray newLines, vtkPoints newPts, vtkDoubleArray outScalars, vtkDoubleArray outVectors, int z)
Protected Attributes
double	GradientThreshold
double	PhiThreshold
double	LinkThreshold